Exhibit 99.1

    iBasis Announces Redemption of its 6 3/4% Convertible Subordinated Notes


    BURLINGTON, Mass.--(BUSINESS WIRE)--Aug. 16, 2005--iBasis, Inc.
(OTCBB: IBAS), a leader in international long distance, VoIP, and
prepaid calling cards, announced today it will redeem all of its
outstanding 6 3/4% Convertible Subordinated Notes due June 2009. The
redemption date will be September 6, 2005. The aggregate principal
amount of Notes outstanding is $32,599,000.
    The redemption price will be $1,000.00 plus accrued interest up to
but not including the redemption date for each $1,000.00 Note
principal amount. The redemption of the Notes will be funded from
existing cash, cash equivalents and short-term marketable investments.
Holders of the Notes will be notified by the Trustee, The Bank of New
York, of specific instructions regarding redemption of the Notes.
    Holders have the right to convert their Notes into iBasis Common
Stock at any time before the close of business on September 2, 2005,
the business day immediately prior to the redemption date. The Notes
are convertible into Common Stock at a conversion price of $1.85 per
share. The Company will pay cash in lieu of fractional shares upon
conversion of the Notes. No accrued interest will be paid upon
conversion of the Notes.

    About iBasis

    Founded in 1996, iBasis (OTCBB: IBAS) is a leading wholesale
carrier of international long distance telephone calls and a provider
of retail prepaid calling services, including the Pingo(TM) web-based
offering (www.pingo.com) and disposable calling cards, which are sold
through major distributors and available at retail stores throughout
the U.S. iBasis customers include many of the largest
telecommunications carriers in the world, including AT&T, Cable &
Wireless, China Mobile, China Unicom, MCI, Sprint, Skype, and
Telefonica. iBasis carried approximately 5 billion minutes of
international voice over IP (VoIP) traffic in 2004, and is one of the
ten largest carriers of international voice traffic in the world(1).
For four consecutive years service providers named iBasis the best
international wholesale carrier in ATLANTIC-ACM's annual International
Wholesale Carrier Report Card(2). iBasis was also ranked among the
fastest-growing technology companies in New England in the 2002, 2003,
and 2004 Technology Fast 50 programs sponsored by Deloitte & Touche.
The Company can be reached at its worldwide headquarters in
Burlington, Massachusetts, USA at 781-505-7500 or on the Internet at
www.ibasis.com.

    iBasis is a registered mark, The iBasis Network and Pingo are
trademarks of iBasis, Inc. All other trademarks are the property of
their respective owners.

    Except for historical information, all of the expectations,
projections and assumptions contained in the foregoing press release,
including those relating to our current expectations regarding the
redemption of the Notes, expected savings in interest expense and use
of cash, constitute forward-looking statements under Section 21E of
the Securities Exchange Act of 1934, as amended, and involve risks and
uncertainties. Important factors that could cause actual results to
differ materially from such forward-looking statements include, but
are not limited to, (i) the extent of adoption of our services and the
timing and amount of revenue and margin generated by these services;
(ii) fluctuations in the market for and pricing of these services; and
(iii) the other considerations described as "Risk Factors" in our most
recent Forms 10-K and 10-Q, and our other SEC filings. We have no
current intention to update any forward-looking statements.

    (1)Telegeography 2005 data compared with iBasis 2004 traffic
volume.

    (2)ATLANTIC-ACM International Wholesale Carrier Report Card -
2002, 2003, 2004, & 2005.



    CONTACT: iBasis, Inc.
             Media:
             Chris Ward, 781-505-7557
             cward@ibasis.net
             or
             Investors:
             Richard Tennant, 781-505-7409
             ir@ibasis.net