(Fortune Magazine) -- As you peruse the Fastest-Growing list, you'll notice two glaring omissions: Google (Charts) and Apple (Charts). The explanations for their absence are simple: A company has to have been trading for at least three years to qualify for the list, and Google went public in August 2004. And Apple has told investors to ignore its recent financial results, pending the conclusion of an internal investigation into how stock options were granted. But a story on growth investing wouldn't be complete without considering the two hottest companies on the planet, so here we go.

The big question for Google is how long it can maintain its blistering growth rate. Boasting the most widely used Internet search engine by far, the company captures a huge chunk of the advertising dollars migrating to the Internet as more people spend more time and money online. But to stay on top, it will have to continue to innovate faster and better than competitors such as Yahoo (Charts) -- and founders Larry Page and Sergey Brin haven't always hit home runs. Google hasn't been successful in integrating new offerings such as blogging and photo-sharing services. Meanwhile big efforts such as Google Earth digital mapping do little to generate additional revenue for the company.

Investors clearly believe the growth will continue. Shares trade at 50 times the past 12 months' earnings, about three times the market multiple. It seems unnecessary to point out that the stock is expensive. It's more interesting to wonder how cheap it might become if the company ever misses a quarter and the momentum investors bail out. That could be a great time to buy.

Apple's situation is more complicated. On June 29, the corporation became the ritziest name ensnared in the stock- options accounting scandal that has now touched more than 100 companies. Apple announced that an internal review had uncovered "irregularities" in the way certain employee stock options were handled between 1997 and 2001. Then it said in early August that it had found additional irregularities, and that all earnings and press releases since September 2002 should no longer be relied upon.

Investors and analysts aren't fazed by the restatements, saying they concern past practices. In fact, the stock is up 20% since late June and retains its premium multiple of 33 times the past 12 months' earnings. Apple's iPod continues its runaway success -- sales are growing 30% a year -- and lately it's been driving increased purchases of Apple personal computers.

It's worth noting that federal prosecutors recently charged three former executives at Comverse Technology (Charts) with fraud related to alleged manipulation of stock option grant dates. There is no indication that the same will happen at Apple -- or that CEO Steve Jobs is personally implicated. Still, until the matter is resolved, this Apple is best left unpicked.