CHICAGO, Sept. 8 /PRNewswire-FirstCall/ -- Archipelago Holdings, Inc. (PCX: AX) today announced its August 2005 market transaction volume data for the Archipelago Exchange (ArcaEx(R)), a facility of the Pacific Exchange. Specifically, in NYSE- listed equity securities, ArcaEx's total trading market share was 3.7% in August 2005, up from 1.8% in August 2004 and up from 3.5% in July 2005.

In AMEX-listed equity securities, ArcaEx's total trading market share was 31.3% in August 2005, up from 26.1% in August 2004 and up from 30.5% in July 2005. ArcaEx's ETF total monthly share volume showed continued year-over-year growth with 2,259.7 (millions of shares) having traded in August 2005 compared to 1,357.2 (millions of shares) traded in August 2004 and up from 1,933.5 (millions of shares) in July 2005.

In Nasdaq-listed equity securities, ArcaEx's total trading market share was 22.8% in August 2005 down from 26.3% in August 2004 and down from 24.1% in July 2005.

    ArcaEx Transaction Volume Data
                                               August       July        August
                                                2005        2005         2004

    Total monthly volume of Nasdaq-listed
    equity securities (millions of shares)      35,810.1   33,681.1   31,481.3

    ArcaEx monthly volume of Nasdaq-listed
    equity securities (millions of shares)(1)    8,177.2    8,124.6    8,294.5

    ArcaEx share of total monthly volume
    of Nasdaq-listed equity securities(%)(2)       22.8%      24.1%      26.3%

    Total monthly volume of NYSE-listed
    equity securities (millions of shares)      43,330.3   38,542.5   33,396.9

    ArcaEx monthly volume of NYSE-listed
    equity securities (millions of shares)(1)    1,593.3    1,340.1      585.0

    ArcaEx share of total monthly volume of
    NYSE-listed equity securities (%)(2)            3.7%       3.5%       1.8%

    Total monthly volume of AMEX-listed
    equity securities (millions of shares)       6,303.8    5,353.8    5,599.5

    ArcaEx monthly volume of AMEX-listed
    equity  securities (millions of shares)(1)   1,972.4    1,635.3    1,462.0

    ArcaEx share of total monthly volume of
    AMEX-listed equity securities (%)(2)           31.3%      30.5%      26.1%

    ArcaEx ETF total monthly share volume
    (millions of shares)(1)                      2,259.7    1,933.5    1,357.2

    ArcaEx monthly customer order volume
    matched internally (%)(3)                      88.7%      88.8%      86.9%

    ArcaEx monthly customer order volume
    routed out  (%)(3)                             11.3%      11.2%      13.1%

    Number of trading days in period                  23         20         22


                        ArcaEx Most Active August 2005
           Symbol                       Share Volume             Market Share
    Nasdaq-100 Index(R)   (QQQQ)        474,336,249                 27.3%
    SPDR(R)               (SPY)         435,512,460                 33.1%
    Microsoft(R)          (MSFT)        317,097,928                 21.9%
    Cisco Systems(R)      (CSCO)        266,175,789                 20.3%
    iShares Russell 2000
    Index                 (IWM)         221,398,849                 43.3%
    Intel(R)              (INTC)        203,451,428                 20.4%
    Semiconductor Holders (SMH)         188,342,500                 45.9%
    Applied Materials     (AMAT)        122,553,107                 25.6%
    Apple Computer        (AAPL)         82,209,512                 24.3%
    Altera                (ALTR)         32,281,097                 28.4%

Additional information on ArcaEx daily, weekly and monthly trading transaction volumes is publicly available in real time through the ArcaVision website accessible via 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 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.

About Archipelago Holdings

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 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
    -0-                             09/08/2005
    /CONTACT:  Press, Margaret Nagle, +1-312-442-7083, or Investor Relations,
Patrick Murphy, +1-312-442-7005, both of Archipelago Holdings/
    /Web site:  http://www.archipelago.com
                http://www.arca-vision.com /
    (AX)

CO:  Archipelago Holdings
ST:  Illinois
IN:  FIN
SU:

PA
-- NYTH166 --
7707 09/08/2005 12:53 EDT http://www.prnewswire.com