[BELL, BOYD & LLOYD LLC LETTERHEAD}
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        70 West Madison Street, Suite 3100 - Chicago, Illinois 60602-4207
                        312.372.1121 - Fax 312.827.8000






KEVIN J. MCCARTHY
312.807.4341
kmccarthy@bellboyd.com



VIA EDGAR

                                  March 3, 2005



Mr. Vincent Distefano
Securities and Exchange Commission
Division of Investment Management
450 Fifth Street, N.W.
Washington, DC  20549


                            CALAMOS INVESTMENT TRUST

Dear Mr. Distefano:

         This letter responds to the comments you conveyed to me on February 18,
2005, regarding the post-effective amendment to the registration statement filed
on behalf of Calamos Investment Trust (the "Trust") on form N-1A in order to
register shares of a new series of the Trust, International Growth Fund (the
"Fund"). For convenience, each of your comments, as we understood them, is
repeated below, with responses immediately following. Where revised disclosure
from the post-effective amendment is included in a response, we have marked the
disclosure to show changes from the original post-effective amendment filing on
December 29, 2004. Those pages of the revised post-effective amendment that
reflect the changes made in response to your comments are attached, and the
changes are marked with the number of the comment to which the particular
revision relates. We are hoping to file a post-effective amendment to the
Trust's registration statement on or before March 11, 2005, so we hope to
resolve any outstanding issues as quickly as possible.

PROSPECTUS

A.       WHAT ARE THE INVESTMENT OBJECTIVES?

         1.       COMMENT: On page 3, please confirm whether the analysis
                  described in the first sentence of the fifth paragraph is the
                  same for all securities of the Fund, including equity, debt
                  and convertibles.










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                       c h i c a g o - w a s h i n g t o n




Mr. Vincent Distefano
March 3, 2005
Page 2



                  RESPONSE: The analysis discussed in the first sentence of the
                  fifth paragraph relates to all of the Fund's securities. To
                  clarify, we will revise the first sentence to read as follows:

                           "When buying and selling the types of securities
                  referenced above, the investment adviser focuses on the
                  issuer's potential for revenue and earning growth and return
                  on capital as well as the sustainability of these factors."

B.       WHAT ARE THE PRINCIPAL RISKS OF INVESTING IN THE FUND?

         2.       COMMENT: On page 4, please add a disclosure in the paragraph
                  entitled "Foreign Securities Risk" describing the types of
                  securities in which the Fund will invest.

                  RESPONSE: The Fund will invest primarily in foreign equity
                  securities, but may also invest in foreign convertible
                  securities, preferred stock, bonds, debentures and notes. We
                  will revise the paragraph to read as follows:

                  "Foreign Securities Risk. The Fund may invest up to 100% of
                  the Fund's net assets in securities of foreign issuers. The
                  Fund will invest primarily in foreign equity securities, but
                  may also invest in foreign convertible securities, preferred
                  stock, bonds, debentures and notes. There are special risks
                  associated with investing in foreign securities that are not
                  typically associated with investing in U. S. companies. These
                  risks include fluctuations in the exchange rates of foreign
                  currencies that may affect the U.S. dollar value of a
                  security, and the possibility of substantial price volatility
                  as a result of political and economic instability in the
                  foreign country. Other risks of investing in foreign
                  securities include: less public information about issuers of
                  securities, different securities regulation, different
                  accounting, auditing and financial reporting standards, and
                  less liquidity in foreign markets than in U.S.
                  markets."

         3.       COMMENT: On page 4, please add a risk regarding the "growth"
                  style of investing.

                  RESPONSE: We will add the following risk to page 4 of the
                  prospectus to read as follows:

                  "Growth Stock Risk. The Fund intends to invest in equity
                  securities of companies that it believes will experience
                  relatively rapid earnings growth. Growth securities typically
                  trade at higher multiples of current earnings than other
                  securities. Therefore, growth securities may be more sensitive
                  to changes in current or expected earnings than other
                  securities. Growth securities also may be more volatile
                  because growth companies usually invest a high portion of
                  earnings in their business, and they may lack the dividends of
                  value stocks that



Mr. Vincent Distefano
March 3, 2005
Page 3



                  can lessen the decreases in stock prices in a falling market.
                  A company may never achieve the earnings expansion the Fund
                  anticipates."

C.       FUND FACTS--WHO MANAGES THE FUNDS?

         4.       COMMENT: On page 7, please provide more detail to the
                  description of the performance adjustment. Namely:

                      - State that the up or down adjustments to the management
                        fee are symmetrical.

                      - State whether or not there is a minimum amount by which
                        the Fund has to outperform the MSCI EAFE Growth Index
                        (the "Index") in order to obtain the performance
                        adjustment. In other words, explain whether the Fund has
                        to outperform the Index by a full 1% in order for the
                        adjustment to take effect. If there is no minimum amount
                        by which the Fund has to outperform the Index, add a
                        risk factor indicating that a small outperformance of
                        the Index by the Fund may be the result of random
                        fluctuations in the market and not necessarily the
                        result of the portfolio managers' expertise.

                      - State whether the Fund will receive a performance fee
                        even if the Fund has a negative return yet still
                        outperforms the Index.

                  RESPONSE: The performance adjustment is symmetrical, meaning
                  the adjustment is made equally whether the Fund outperforms or
                  underperforms the Index. The minimum amount by which the Fund
                  has to outperform the Index to obtain a performance adjustment
                  is set forth in 1% increments. Specifically, the base fee will
                  either be decreased or increased 1/12th of 0.03% for each full
                  1% increment amount by which the Fund outperforms or
                  underperforms the Index. As a result, we do not believe that
                  risk disclosure regarding the impact that random fluctuations
                  in the market may have on the performance fee is warranted.
                  Lastly, the Fund will receive a performance fee if its return
                  is negative, but it outperforms the Index. To reflect this
                  additional detail, we will edit this section, and similar
                  disclosures in the Statement of Additional Information, to
                  read as follows:

                           "Subject to the overall authority of the board of
                  trustees, Calamos Advisors provides continuous investment
                  supervision and management to the Fund under a management
                  agreement and also furnishes office space, equipment and
                  management personnel. The Fund pays Calamos Advisors a fee
                  based on average daily net assets that is accrued daily and
                  paid on a monthly basis, except for the performance fee, which
                  will be accrued and paid on monthly basis beginning _____. The
                  fee paid by the Fund is determined by utilizing a base fee




Mr. Vincent Distefano
March 3, 2005
Page 4


                  and then applying a performance adjustment. The performance
                  adjustment equally increases or decreases the management fee,
                  on a monthly basis, by 1/12 of 0.03% of the Fund's average
                  daily net assets for each full 1% increment amount by which
                  the Fund outperforms or underperforms the MSCI EAFE Growth
                  Index ("Index"), respectively. The base fee is at the annual
                  rate of 1.00% of the first $500 million of the Fund's average
                  daily net assets, 0.95% of the next $500 million of average
                  daily net assets, 0.90% of the next $5 billion of average
                  daily net assets (average daily net assets in excess of $1
                  billion to $6 billion), 0.88% of the next $5 billion of
                  average daily net assets (average daily net assets in excess
                  of $6 billion to $11 billion), 0.86% of the next $5 billion of
                  average daily net assets (average daily net assets in excess
                  of $11 billion to $16 billion), 0.84% of the next $5 billion
                  of average daily net assets (average daily net assets in
                  excess of $16 billion to $21 billion), 0.82% of the next $5
                  billion of average daily net assets (average daily net assets
                  in excess of $21 billion to $26 billion) and 0.80% of average
                  daily net assets in excess of $26 billion.

                           The performance adjustment rate is calculated by
                  comparing over the performance period the Fund's performance
                  to that of the Index. The performance period will begin at the
                  beginning of the first full month of operation and will
                  eventually include 36 months. The performance adjustment will
                  not take effect until ______.

                           The maximum annualized performance fee adjustment
                  rate is plus or minus 0.30% of the Funds average daily net
                  assets over the performance period. The performance adjustment
                  rate is divided by twelve and multiplied by the Fund's average
                  daily net assets over the performance period, and the
                  resulting dollar amount is then added to or subtracted from
                  the base fee. Calamos Advisors may receive a positive
                  performance adjustment even if the Fund has a negative return
                  over a performance period if it otherwise outperforms the
                  Index during that period."

D.       FUND FACTS--TRANSACTION INFORMATION--SHARE PRICE

         5.       COMMENT: On page 13, please delete from the first sentence of
                  the fourth paragraph the phrase "some or all of" and the word
                  "materially".

                  RESPONSE:  We will edit the sentence to read as follows:

                  "The Fund may use fair value pricing if the value of the
                  Fund's securities have been affected by events occurring
                  before the Fund's pricing time but after the close of the
                  primary markets or exchanges on which the security is traded."





Mr. Vincent Distefano
March 3, 2005
Page 5



E.       FUND FACTS--TRANSACTION RESTRICTIONS

         6.       COMMENT: On page 14, in the first sentence of the second
                  paragraph, under the heading "Transaction Restrictions",
                  please change the word "trading" to "purchase" on the theory
                  that the Fund cannot prohibit a shareholder from redeeming
                  shares.

                  RESPONSE:  We will edit the sentence to read as follows:

                  "The Fund may, in its discretion, suspend, and may permanently
                  terminate, the purchase or exchange privileges of any investor
                  who engages in trading activity that it believes would be
                  disruptive to the Fund."

STATEMENT OF ADDITIONAL INFORMATION

A.       COMMENT: On page 32 of the SAI, please change the heading from
         "Disclosure to Rating/Ranking Agencies" to "Non-Public Disclosure" and
         make certain that all discussion regarding non-public disclosure is
         covered under that heading.

         RESPONSE: We will add the heading "Non-Public Disclosure" prior to
         "Disclosure to Rating/Ranking Agencies" and retain the subheadings
         currently in place as they all relate to non-public disclosure.

B.       COMMENT: On page 32 of the SAI, under the subheading entitled
         "Disclosure to Service Providers", state, by category of persons, who
         makes the determination to approve non-public disclosures not
         specifically covered by the Trust's portfolio holdings disclosure
         policy.

         RESPONSE: On page 32 of the SAI, we will add the following sentence to
         the end of the second paragraph under the section entitled "Disclosure
         to Service Providers":

         "Any such disclosure must be approved in writing by an officer of the
         Fund, after consultation with Calamos Advisors' Legal/Compliance
         Department."

C.       COMMENT: On page 32 of the SAI, please state whether service providers
         are prohibited from trading on portfolio holdings information.

         RESPONSE: On page 32 of the SAI, we will add the following sentence to
         the end of the first paragraph under the section entitled "Disclosure
         to Service Providers":

         "The Fund's service providers have a duty to keep the Fund's nonpublic
         information confidential either through written contractual
         arrangements with the Fund or the Adviser, or by the nature of their
         role with respect to the Fund."





Mr. Vincent Distefano
March 3, 2005
Page 6



D.       COMMENT: On page 34 of the SAI, the third paragraph states that the
         Board can change the index for comparison of the performance fee. It is
         the Commission's view that such a change would be material and
         fundamental and that the Fund would have to get shareholder approval to
         make the change.

         RESPONSE: We will revise the third paragraph on page 34 to read as
         follows:

         "If the board of trustees determines that another index is appropriate
         for International Growth Fund, it may designate a successor index to be
         substituted, subject to approval by shareholders."

                                    * * * * *
         We believe that this information responds to all of your comments.
Please call me to confirm the adequacy of our responses at 312/807-4341.

                                          Very truly yours,

                                          /s/ Kevin J. McCarthy
                                          -----------------------------------

                                          Kevin J. McCarthy

KJM:aap
Enclosures