(Business 2.0) – Tech is back--and the sector's fastest-growing public companies are leading the charge. During the past three years, the companies in this elite group have increased sales by an average of 33 percent a year, stoked profits by 86 percent, and raised cash flow from operations by 83 percent. Wall Street has applauded, sending the Business 2.0 100's shares up an average of 38 percent in 2005.

What's behind the blazing numbers? A few big trends underscore this year's rankings. Automating the $2 trillion U.S. health-care industry continues to create giant opportunities, as 16 of the 100 companies are helping to speed up patient care, medical testing, or drug discovery. The rapid spread of 3G wireless networks also boosted a variety of players, from Motorola and Qualcomm to F5 Networks. And advertising has replaced retailing as the Web sector to watch: eBay, despite adding 3,500 employees and $1.3 billion in sales, couldn't keep pace and fell from 14th on last year's list to 92nd here, while Web-ad giants aQuantive and Digitas made their B2 100 debuts.

Best of all, the growth these days isn't just coming from cost cutting. Job seekers will be happy to know that the companies on this list hired more than 70,000 people last year, expanding their payrolls by an average of 16 percent. Think of it as a return to the late '90s, minus the goatees and foosball tables.

[*] Merge is restating these figures due to accounting problems.

HOW WE RANK THEM To find the B2 100, we screened a universe of more than 2,000 tech companies that have been publicly traded on a U.S. stock exchange for at least three years, have a market capitalization of at least $50 million, and have had positive operating cash flow over the past 12 months. Zacks Investment Research of Chicago ranked the resulting list using four financial criteria: growth in revenue, profit, and operating cash flow during the past three years, and the 12-month stock return as of Dec. 31, 2005. Cash flow growth counts for 40 percent of a company's ranking. Each of the other criteria counts for 20 percent.

The B2 100's hottest stock? No. 7 aQuantive. Its shares nearly tripled in 2005 as investors jumped on the online-advertising boom.

Consumers and companies alike are demanding more and more data storage, a boon to several B2 100 suppliers.

Cost-cutting pressures and the push for automation in hospitals made medical companies the top category on the list.

Motorola, the B2 100's biggest company, saw sales jump by $5.5 billion--more than the total sales of all but eight of the others.

Patrick Baltatzis, Saheli S.R. Datta, Joseph De Avila, Julia Feldmeier, Michael Fitzhugh, David Goldenberg, Susanna Hamner, David Jacobson, Heidi Ledford, Michal Lev-Ram, Jeff Nachtigal, Snigdha Sen, Michael Yunfeng Zhao and Moming Zhou contributed to this article.