Instinet Group Announces May 2004 Transaction Information: INET Increases NASDAQ-Listed And U.S. Exchange-Listed Market Share

Instinet Group Incorporated (NASDAQ: INGP) today announced May 2004 transaction data for its two major business segments: Instinet, the Institutional Broker and INET, the Electronic Marketplace.

In May 2004, Instinet's total average daily U.S. equity share volume was 104 million shares, which represents a 2.7% share of the U.S. equity market. This compares to 113 million shares, or 2.7% of the U.S. equity market, in April 2004, and 97 million shares, or 2.5% of the U.S. equity market, in May 2003.

In May 2004, INET's total matched average daily U.S. equity share volume was 507 million shares, or 13.4% of the U.S. equity market. This volume consisted of 426 million shares of NASDAQ-listed stocks, or a 25.6% share of the NASDAQ-listed market, and 81 million shares of U.S. exchange-listed stocks, or 3.8% of the U.S. exchange-listed market.

This compares to INET's total matched average daily share volume of 555 million in April 2004, or 13.4% of the U.S equity market, consisting of 481 million shares of NASDAQ-listed stocks, or a 24.8% share of the NASDAQ-listed market, and 74 million shares of U.S. exchange-listed stocks, or 3.4% of the U.S. exchange-listed market.

In May 2003, INET's total matched average daily share volume was 534 million shares, or 13.8% of the U.S equity market, consisting of 485 million shares of NASDAQ-listed stocks, or a 26.3% share of the NASDAQ-listed market, and 49 million shares of U.S. exchange-listed stocks, or 2.4% of the U.S. exchange-listed market.

Instinet Group also reports monthly operating data on its website at www.instinetgroup.com under the heading "Investor Relations - Instinet Trading Activity."

	May 2004	April 2004	May 2003 (3)
# of Trade Days	20	21	21
Instinet
Total U.S. equity average daily volume (million shares)	104	113	97
Share of total U.S. equity market	2.7%	2.7%	2.5%
INET - Matched Average Daily Volume (2)
Nasdaq-listed equity share volume (million shares)	426	481	485
Share of total Nasdaq market	25.6%	24.8%	26.3%
U.S. exchange-listed share volume (million shares)	81	74	49
Share of total U.S. exchange-listed market	3.8%	3.4%	2.4%
Total U.S. equity share volume (million shares)	507	555	534
Share of total U.S. equity market	13.4%	13.4%	13.8%

Monthly totals may not reflect weekly data, which are preliminary. The number of trading days in each period takes account of U.S. market holidays and any other U.S. market closings.

For a description of how we calculate Instinet's transaction volumes, see "Management's Discussion and Analysis of Financial Condition and Results of Operations - Calculation of Volume - Instinet, the Institutional Broker" in our Form 10-Q for the fiscal quarter ended March 31, 2004.
For a description of how we calculate INET's transaction volumes, see "Management's Discussion and Analysis of Financial Condition and Results of Operations - Calculation of Volume - INET, the Electronic Marketplace " in our Form 10-Q for the fiscal quarter ended March 31, 2004.
Represents Inet ATS, Inc. volume, including volume from ProTrader Securities L.P. beginning the week ended 10/5/01 through 7/22/03.

Instinet has experienced significant seasonality in its business, and period-to-period comparisons of operating results are not necessarily meaningful, nor are the results for any period necessarily indicative of results for any future period.