NEW YORK (CNN/Money) – Fortune magazine has released its annual list of America's fastest growing companies, led this year by airport x-ray machines maker InVision Technologies.

eResearch Technology, a Philadelphia-based company that makes software used to track test data, ranked No. 2.

Twelve companies on the 2004 list are Fortune 500 companies. The average market value of all companies on this year's list is $4.8 billion.

The 100 companies that made the cut sold nearly $262 billion in goods and services last year.

But history has proven that fastest growing doesn't always mean long-lasting or most profitable.

"In its first 13 years, through boom and bust, one lesson became clear: Fast growing does not follow a formula," said Fortune writer Wilfried Eckl-Dorna in his introduction to the list. "Hot sectors emerge and cool off. Technology evolves. Tastes change."

Certain trends have appeared over the years. Health care companies were some of the fastest-growing from 1991-1994, and the next three years saw the rise of the oil drillers.

And of course technology companies, with their meteoric rise before their eventual bust, took center stage throughout the late 1990s.

Since the list was first published in 1991, 28 companies have appeared four times, while nine have appeared five times.

Dell is the only company to have appeared seven times, and pharmacy benefits manager Express Scripts and Starbucks made the list six times. But this year none of these three companies made the cut.

See the complete list at Fortune.com.

Fortune bases its list of fastest growing companies on data from Zacks Investment Research, which looks at companies with a minimum market capitalization of $50 million, at least $50 million in revenues over the past four quarters and at least 20 percent annual growth in sales and earnings over the past three years.

Fortune then factors in total stock market return to come up with the final list.