Micromuse Listed On America's Fastest Growing Companies Index.

Business Editors & High Tech Writers

SAN FRANCISCO--(BUSINESS WIRE)--April 19, 2001

Individual Investor Group Touts Micromuse

As "Best Seller" and "Dearest" Stock Among 500 U.S. Companies

Micromuse Inc. (Nasdaq:MUSE), the leading provider of realtime fault management and service assurance software, today announced that it has been named to the America's Fastest Growing Companies(TM) (AFGC(TM)) Index by Individual Investor Group, Inc., the publisher of Individual Investor Magazine and individualinvestor.com.

The AFGC(TM) Index, which appears in the April 2001 issue of Individual Investor Magazine, tracks the 500 fastest growing U.S. companies based on a percentage of earnings-per-share growth in their most recent quarters.

Published annually since 1998, the AFGC Index bills itself as the first real barometer of America's emerging market of fast-growing, small-cap stocks and is representative of companies listed on all three major exchanges. To be considered for inclusion, companies must have a market value between $100 million and $2 billion and show at least 50% earnings-per-share growth in their most recent quarters. Using a market capitalization weighting methodology, the Index measures for price-performance only and is rebalanced at the end of each quarter. The Index is calculated and disseminated by the American Stock Exchange under the ticker symbol NDI. "We're honored to be recognized by Individual Investor on this year's list of fastest growing companies," said Greg Brown, Chairman & CEO of Micromuse. "Our solid record of consistent growth and strong performance within the service provider and enterprise market segments can be attributed to the dedication of our people and our constant focus on our customers' needs."

Micromuse was listed in the Index's Top 10 "Best Sellers" - those companies with the highest compound annual sales growth over the past three years - and was the number one "Dearest" stock indicating those companies investors expect to continue rapid growth.

The AFGC Index has been licensed to Nuveen Investments, a wholly owned subsidiary of The John Nuveen Company (NYSE:JNC) for the creation of an exchange-traded fund similar to the Nasdaq-100 Index Tracking Stock and the Standard & Poor's Depository Receipts. Pending final regulatory approval, the AFGC fund will trade on the American Stock Exchange.

About Micromuse

Micromuse Inc. (Nasdaq:MUSE) is the leading provider of realtime fault management and service assurance software. Micromuse's recent list of awards include the TeleStrategies OSS Excellence Award for Best New Product for the Netcool(R)/Visionary(TM) application, and Web Hosting Magazine Editor's Choice Award. In addition, Micromuse has been recognized in the Forbes 500, Bloomberg's Top 100 Stocks, the Barron's 500, Deloitte & Touche's Technology Fast 500 and the San Francisco Chronicle 500. Micromuse customers include AT&T, BT, Cable & Wireless, Cellular One, Charles Schwab, Deutsche Telekom, Digex, EarthLink, GTE, ITC DeltaCom, MCI Worldcom, NextLink, One2One, XO Communications and a number of financial investment concerns. Headquarters are located at 139 Townsend Street, San Francisco, Calif. 94107; [phone]. The Web site is at www.micromuse.com

America's Fastest Growing Companies is a registered trademark of the Individual Investor Group, Inc.

Netcool and Micromuse are registered trademarks of Micromuse Ltd. All other trademarks and registered trademarks in this document are the properties of their respective owners. Any statements contained in this press release that do not describe historical facts may constitute forward-looking statements as that term is defined in the Private Securities Litigation Reform Act of 1995. Any forward-looking statements contained herein are based on current expectations, but are subject to a number of risks and uncertainties.

The factors that could cause actual future results to differ materially from the forward-looking statements include the following: fluctuations in customer demand, the Company's ability to manage its growth (including the ability to hire sufficient sales and technical personnel), the risks associated with the expansion of the Company's distribution channels, the risk of new product introductions and customer acceptance of new products; the rapid technological change which characterizes the Company's markets, the risks associated with competition, the risks associated with international sales as the Company expands its markets, and the ability of the Company to compete successfully in the future, as well as other risks identified in the Company's Securities and Exchange Commission Filings, including but not limited to those appearing under the caption "Risk Factors" in the Company's most recent Quarterly Reports on Form 10-Q and on Form 10-K on file with the Securities and Exchange Commission and available on the Company's Web site.