CD RADIO INC.
                            (a Delaware Corporation)

                $125,000,000 aggregate principal amount of 8 3/4%
                     Convertible Subordinated Notes due 2009

                                 TERMS AGREEMENT
                                 ---------------

                                                              September 23, 1999
To:      CD Radio Inc.
         1221 Avenue of the Americas, 36th Fl.
         New York, NY 10020

Ladies and Gentlemen:

     This is a Terms Agreement referenced in the Form Underwriting Agreement,
filed as an Exhibit to Registration Statement No. 333-86003, the terms of which
are hereby incorporated herein. We understand that CD Radio Inc., a Delaware
corporation (the "Company"), proposes to issue and sell $125,000,000 aggregate
principal amount of its 8 3/4% convertible subordinated debt securities (the
"Underwritten Securities"). Subject to the terms and conditions set forth or
incorporated by reference herein, we the underwriters named below (the
"Underwriters") offer to purchase, severally and not jointly, the principal
amount of Underwritten Securities opposite our names set forth below at the
purchase price set forth below, and a proportionate share of Option Underwritten
Securities set forth below, to the extent any Underwritten Securities or Option
Underwritten Securities are purchased.







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                                                                                  Principal Amount
                                                                                   of Underwritten
Underwriter                                                                          Securities
- -----------                                                                       ----------------
                                                                               
Merrill Lynch, Pierce, Fenner & Smith Incorporated.......................            $ 62,500,000
Lehman Brothers Inc......................................................              25,000,000
Banc of America Securities LLC...........................................              17,188,000
Bear, Stearns & Co. Inc..................................................              20,312,000
                                                                                  ---------------
                           Total.........................................            $125,000,000
                                                                                  ===============




           The Underwritten Securities shall have the following terms:




                                             Debt Securities
                                             ---------------
                                 
Title:                              Convertible Subordinated Notes due 2009

Rank:                               The Notes will be unsecured obligations of CD Radio and will be
                                    subordinated to existing and future senior indebtedness.  The
                                    Notes will be  effectively subordinated to the indebtedness and
                                    other obligations of the Company's subsidiaries.

Rating:                             CCC-

Aggregate principal amount:         $125,000,000

Principal amount of Option
  Underwritten Securities:          The Underwriters have an option to purchase up to an additional
                                    $18,750,000 aggregate principal amount of the Underwritten
                                    Securities (the "Option Underwritten Securities") at the
                                    public offering price, less underwriting discount, within 30
                                    days from September 23, 1999 to cover over-allotments.

Denominations:                      $1,000 principal amount and integral multiples thereof

Currency of payment:                US dollars

Interest rate or formula:           8.75%

Interest payment dates:             payable semiannually in arrears on March 29 and September 29
                                    of each year commencing March 29, 2000

Regular record dates:               March 14 and September 14

Stated maturity date:               September 29, 2009

Redemption provisions:              The Company may not redeem the Notes prior to September 29, 2002.
                                    On or after such date, the Notes are redeemable for cash at any
                                    time at the Company's option, in whole or in part, at redemption
                                    prices set forth below, plus accrued and unpaid interest to the
                                    date of redemption. Notwithstanding the above, the Company will
                                    not be entitled to redeem the Notes after September 29, 2002,
                                    unless the last reported sale price for the Company's common
                                    stock is at least 150% of the conversion price set









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                                    forth below for at least 20 trading days within a period of 30
                                    consecutive days ending within five trading days of the call
                                    for redemption.

                                    The table below shows redemption prices of a Note during each
                                    twelve-month period set forth below:


                                            Period                                               Redemption Price
                                            ------                                               ----------------
                                                                                            
                                    September 29, 2002 through September 28, 2003.........        106.125%
                                    September 29, 2003 through September 28, 2004..........       105.250%
                                    September 29, 2004 through September 28, 2005..........       104.375%
                                    September 29, 2005 through September 28, 2006..........       103.500%
                                    September 29, 2006 through September 28, 2007..........       102.625%
                                    September 29, 2007 through September 28, 2008..........       101.750%
                                    Thereafter.............................................       100.875%

Sinking fund requirements:          None

Conversion provisions:              Each Note will be convertible, at the option of the holder, at any
                                    time on or prior to maturity, unless previously redeemed or
                                    otherwise purchased, into shares of the Company's common stock
                                    at a conversion rate of 35.134 shares per $1,000 principal amount
                                    of Notes, or a conversion price of $28.4625 per share of common
                                    stock.  The conversion rate will be subject to adjustment upon the
                                    occurrence of certain events affecting the Company's common
                                    stock.  Subject to certain exceptions, upon conversion, the holder
                                    will not receive any cash payment representing any further
                                    interest; such accrued cash interest will be deemed paid by the
                                    shares of common stock received by the holder on conversion.

Listing requirements:               None

Black-out provisions:               None

Fixed or Variable Price
  Offering:                         Fixed Price Offering

                                    If Fixed Price Offering, initial public offering price per
                                    $1,000 principal amount: 100% of the principal amount,
                                    plus accrued interest, if any, from September 29, 1999.

Purchase price per Note:            97% of principal amount, plus accrued interest, if any, from
                                    September 29, 1999.

Form:                               The Notes will initially be issued in fully registered book-
                                    entry form and will be represented by one or more permanent
                                    global Notes without coupons deposited with a custodian for
                                    and registered in the name of a nominee of The Depository
                                    Trust Company ("DTC") in New York, New York.

Other terms and conditions:         All notices and other communications hereunder shall be in
                                    writing and shall be deemed to have been duly given if mailed or
                                    transmitted by any standard form of telecommunication.  Notices
                                    to the Underwriters shall be directed to the Underwriters at
                                    Merrill Lynch & Co., North Tower, World Financial Center, New
                                    York, New York 10281, attention of Robert Kramer; notices to
                                    the Company shall be directed to the Company at 1221 Avenue
                                    of the Americas, 36th Floor, New York, New York 10020,








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                                    attention of Patrick L. Donnelly, Senior Vice President, General
                                    Counsel and Secretary.

Closing date and location:          September 29, 1999

                                    Cravath, Swaine & Moore
                                    Worldwide Plaza
                                    825 Eighth Avenue
                                    New York, NY 10019-7475









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     Please accept this offer by signing a copy of this Terms Agreement in the
space set forth below and returning the signed copy to us.


                                    Very truly yours,

                                    MERRILL, LYNCH, PIERCE, FENNER &
                                    SMITH INCORPORATED


                                    By /s/ Marilyn J. Pugliese
                                      ---------------------------------
                                      Name:  Marilyn J. Pugliese
                                      Title: Authorized Signatory

                                    Acting on behalf of itself and the other
                                    named Underwriters.

Accepted:

CD RADIO INC.


By /s/ Patrick L. Donnelly
  -----------------------------
  Name:  Patrick L. Donnelly
  Title: Senior Vice President,
         General Counsel and
         Secretary