(FORTUNE Magazine) -- In the spring of 2002, juicemaker Hansen Natural launched a teen-targeted energy drink named Monster. By the end of 2003, the company's stock had doubled, and its sales were up 20%.

Then things really took off. Since the beginning of 2004, Hansen Natural's stock has risen a Google-stomping 3,900%, to $170. And the popularity of its main product is still growing: In the first quarter of 2006, Monster (which accounted for the majority of the company's $138 million in sales) helped boost Hansen's profits by 140%. On July 7, Hansen will split its stock four-for-one, putting an exclamation point on a mind-blowing run of success for shareholders.

Hansen's meteoric rise, however, has attracted plenty of professional skeptics. Short-sellers lured by its lofty P/E - the stock trades at 53 times trailing earnings - have flocked to the beverage company. Almost 20% of its outstanding shares have been sold short. But ironically the heavy shorting has helped keep the stock riding high in recent months. "There is no doubt," says Canaccord Adams analyst Scott Van Winkle, "that when there are fewer shares out there floating because a good percentage are borrowed, it has a positive impact on the share price."

Hansen fans say there's plenty to be bullish about. The energy drink segment is booming - up 80% last year, according to the Beverage Marketing Corp. And Hansen has grabbed share from the granddaddy of the category, Red Bull, through size variety and new products like Khaos, a "juice-Monster hybrid."

Jason Schrotberger, an avid Monster drinker and portfolio manager at Turner Investment Partners, which holds a 2% position in Hansen, says that another key ingredient of Monster's success is "street cred." Hansen has won over cool kids by promoting athletes like Mike Metzger, the "godfather of freestyle motorcross," bands such as Bullets and Octane, and events like the XXL big-wave surfing contest. A new distribution deal with Anheuser-Busch could give sales another lift. But Van Winkle believes that Hansen's margins have peaked. If so, it could be a good excuse for investors to take profits. And the shorts might finally get their Monster-sized selloff.