(Fortune Magazine) -- The Petro-fication of our 100 Fastest-Growing Companies list continues apace. Each year our ranking provides a snapshot of America's economy, and this year the picture is drenched in oil. Last year 18 energy firms cracked the top 100 -- up from four in 2000. Oil prices have soared ever higher, and now more than a third of our roster -- 34 companies -- are in the energy biz. Among them is our No. 1, Vaalco Energy (Charts) of Houston, an exploration and production company that saw profits soar at an astonishing rate of 147% annually over the past three years, while its stock returned a total of 906%.

But oil is hardly the whole story. Computer and biotech firms make their usual strong showing, and there are some surprising names, like the Chicago Mercantile Exchange (Charts), No. 81. Powered by its popular Eurodollar contract and other financial products, the 108-year-old Merc has been burning up the track since it went public in 2002, with its stock gaining 619% in three years. Catering to Americans' obsession with how they look (and how well they see) has been remarkably lucrative: LCA-Vision (Charts), a laser-surgery provider, lands at No. 5, followed closely by Palomar Medical Technologies (Charts), which makes laser devices used in cosmetic skin treatments. Giving more evidence that the housing bubble is rapidly deflating, only two homebuilders made the cut: Toll Brothers (Charts) at No. 98, and Meritage Homes (Charts) at No. 99. Last year there were four homebuilders and two land developers on the list. As the homebuilders demonstrate, sustaining explosive growth is nearly impossible. But for those keeping score, retailer Chico's (Charts) (No. 100), IT services provider Cognizant (Charts) (No. 31), and Meritage (Charts) tie for the longest current streak on the list, with four consecutive years.

Apple (Charts) and Google (Charts) are two of the fastest growers around these days. And the Silicon Valley stars are becoming increasingly close. Google CEO Eric Schmidt recently joined Apple's board, suggesting a broader alliance between the two staunch Microsoft foes, which also happen to be the two most prolific Silicon Valley innovators of recent years. The companies have something else in common: Neither one is on our list. Thanks to robust growth led by the iPod, Apple was slated to make its very first appearance. But the company has announced that it will probably have to restate earnings because of questions about the timing of stock option grants, so we had to drop it. Google just needs more time: It has been a public company for only two years, and our threshold is three. We're eager to see where it lands in next year's honor roll.

We begin this year's guide to America's elite performers on the following page with the list itself. From there you can move to "Playing With Fire," where we give investment advice on the ten largest companies (by market cap) on the list--plus Apple and Google. The Big Ten include familiar giants -- biotech firm Genentech (No. 79), making its third run on the list, as well as Internet-portal powerhouse Yahoo (Charts) (No. 19) and energy stalwart ConocoPhillips (No. 75), which both appear for the second consecutive time. The booklet that follows offers a look back at five outfits, including Amgen, Papa John's, and Adobe, that once lived life in the fast lane and, while no longer on our list, have made a successful transition to more moderate but sustainable growth.

The Top 10

1. Vaalco Energy

2. Hansen Natural

3. Armor Holdings

4. Southern Copper

5. LCA-Vision

6. Palomar Medical Technologies

7. Amedisys

8. Edge Petroleum

9. Maverick Tube

10. Nucor