CHICAGO, June 10 /PRNewswire-FirstCall/ -- Archipelago Holdings, Inc. (PCX: AX) today announced its May 2005 market transaction volume data for the Archipelago Exchange (ArcaEx(R)). Specifically, in NYSE- listed equity securities, ArcaEx's total trading market share was 3.4% in May 2005, up from 1.4% in May 2004 and up from 3.2% in April 2005.

In AMEX-listed equity securities, ArcaEx's total trading market share was 31.0% in May 2005, up from 22.2% in May 2004 and up from 29.0% in April 2005. ArcaEx's ETF total monthly share volume showed continued year-over-year growth with 2,008.0 (millions of shares) having traded in May 2005 compared to 1,398.0 (millions of shares) traded in May 2004 and was down from 2,213.0 (millions of shares) in April 2005.

In Nasdaq-listed equity securities, ArcaEx's total trading market share was 23.1% in May 2005 down from 26.0% in May 2004 and down from 23.6% in April 2005.

     ArcaEx Transaction Volume Data

                                          May         April       May
                                          2005        2005        2004

    Total monthly volume of
     Nasdaq-listed equity
     securities (millions of
     shares)                            35,677.0    38,991.8    33,273.2
    ArcaEx monthly volume of
     Nasdaq-listed  equity
     securities (millions of
     shares) (1)                         8,241.3     9,218.1     8,636.1
    ArcaEx share of total monthly
     volume of Nasdaq-listed
     equity securities (%)(2)               23.1 %      23.6 %      26.0 %
    Total  monthly volume of
     NYSE-listed equity securities
     (millions of shares)               40,613.9    44,543.4    36,824.0
    ArcaEx monthly volume of
     NYSE-listed equity securities
    (millions of shares)(1)              1,396.4     1,445.5       520.9
    ArcaEx share of total monthly
     volume of NYSE-listed  equity
     securities (%)(2)                       3.4 %       3.2 %       1.4 %
    Total monthly volume of
     AMEX-listed  equity
     securities (millions of
     shares)                             5,224.7     6,159.7     6,783.9
    ArcaEx monthly volume of
     AMEX-listed equity
     securities (millions of
     shares) (1)                         1,619.4     1,787.2     1,507.6
    ArcaEx share of total monthly
     volume of AMEX-listed equity
     securities (%)(2)                      31.0 %      29.0 %      22.2 %
    ArcaEx ETF total monthly
     share volume (millions of
     shares)(1)                          2,008.0     2,213.0     1,398.0
    ArcaEx monthly customer order
     volume matched internally
     (%)(3)                                 88.9 %      88.9 %      86.6 %
    ArcaEx monthly customer order
     volume routed out  (%)(3)              11.1 %      11.1 %      13.4 %
    Number of trading days in
     period                                   21          21          20


                               ArcaEx Most Active May 2005

    Symbol                                     Share Volume     Market Share
    Nasdaq-100 Index(R) (QQQQ)                 529,792,670             28.0 %
    SPDR(R)  (SPY)                             383,379,335             29.2 %
    Microsoft(R)  (MSFT)                       274,298,111             21.4 %
    Intel(R) (INTC)                            268,641,632             20.6 %
    Semiconductor Holdrs(sm) (SMH)             257,974,900             53.9 %
    Cisco Systems(R) (CSCO)                    245,510,863             19.1 %
    Energy Select SPDR(R) (XLE)                177,973,937             55.7 %
    Oracle(R) (ORCL)                           166,815,848             20.1 %
    Sun(R) Microsystems (SUNW)                 124,654,851             19.1 %
    Siebel Systems   (SEBL)                    123,825,527             25.2 %

Additional information on ArcaEx daily, weekly and monthly trading transaction volumes is publicly available in real time through the ArcaVision website accessible via http://www.archipelago.com. Additional data and enhanced functionality can be obtained through a free subscription to ArcaVision. Investors and ArcaEx clients can subscribe to ArcaVision at http://www.arca-vision.com.

    (1) For purposes of calculating monthly transaction volume on ArcaEx, we
        include all shares that are "handled" on ArcaEx for the month.
        Handled shares include both shares that are bought and sold during the
        month within our internal liquidity pool and shares that are routed to
        external market centers for execution.

    (2)  ArcaEx monthly market share is calculated based on the number of
         shares handled on the ArcaEx system during the month as a percentage
         of total monthly volume. Total monthly volume is based on the number
         of shares of equity securities traded during the month on Nasdaq,
         AMEX or the NYSE, including, if applicable, exchange-traded funds, as
         reported in the consolidated tape.  The "consolidated tape" provides
         last sale price and volume of equity securities transactions to the
         public.

    (3)  In computing the percentage of monthly client order volume matched
         internally and the monthly percentage of customer order volume
         routed out, we calculate the percentage based on the volume of
         individual customer orders, not the volume of matched trades (i.e.,
         only counting one side of a matched transaction). For example, we
         calculate two customer orders matched internally on our system as
         two customer orders matched internally, and we include the volume of
         both the buy order and the sell order in computing our percentages
         of monthly customer order volume matched internally and routed out.
         We calculate one customer order routed to an external market center
         (which will be matched with an order at that other market center) as
         one outbound trade or one customer order. We calculate one customer
         order routed to us from an external market center and matched with
         an order on our system as one inbound trade or one customer order.

Archipelago Holdings (PCX: AX) operates The Archipelago Exchange(R) (ArcaEx(R)) the first totally open all- electronic stock exchange in the United States. ArcaEx trades all Nasdaq-listed equity securities and exchange listed equity securities, including those listed on the New York Stock Exchange(R), American Stock Exchange(R), and Pacific Exchange(R). In addition to offering core execution services, ArcaEx provides corporate clients with listing services and innovative data products. In 2004, Archipelago launched ArcaVision to provide corporate and trading clients with more transparent market data, analytical tools and access to market-wide and ArcaEx specific trading information. Archipelago Holdings completed its initial public offering in August 2004. For more information please visit http://www.archipelago.com.

ArcaEx's, past transaction performance is not necessarily indicative of its future results. Periodically, ArcaEX's transaction performance will experience fluctuations due to unforeseen factors effecting trading activity, including seasonality, general economic, political and market conditions, unforeseen market closures or other disruptions in trading. A description of the factors that may influence ArcaEx's volume of securities transactions are identified in the Company's filings with the Securities Exchange Commission, including its Report on Form 10-K for the fiscal year ending December 31, 2004 which is available on the Company's website at http://www.archipelago.com. Certain statements in this press release may contain forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. These statements are based on Archipelago's current expectations and involve risks and uncertainties that could cause Archipelago's actual results to differ materially from those set forth in the statements. There can be no assurance that such expectations will prove to be correct. Factors that could cause Archipelago's results to differ materially from current expectations include: general economic and business conditions, industry trends, competitive conditions, regulatory developments as well as other risks or factors identified in the Company's filings with the Securities Exchange Commission, including its Report on Form 10-K for the fiscal year ending December 31, 2004 which is available on the Company's website at http://www.archipelago.com. You should not place undue reliance on forward- looking statements, which speak only as of the date of this press release. Except for any obligation to disclose material information under the Federal securities laws, Archipelago undertakes no obligation to release publicly any revisions to any forward-looking statements to reflect events or circumstances after the date of this press release.

     Archipelago Contacts:

     Margaret Nagle - Press
     312-442-7083

     Patrick Murphy - Investor Relations
     312-442-7005

SOURCE  Archipelago Holdings, Inc.
    -0-                             06/10/2005
    /CONTACT:  Margaret Nagle - Press, +1-312-442-7083, or Patrick Murphy -
Investor Relations, +1-312-442-7005/
    /Web site:  http://www.archipelago.com /

CO:  Archipelago Holdings, Inc.
ST:  Illinois
IN:  FIN
SU:

BV
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1581 06/10/2005 10:10 EDT http://www.prnewswire.com