"Put that tiger back in your tank!" Natural Heritage Enterprises urges at the top of its Web page. A blurry digital kitten morphs into a puma below. A cartoon man in a suit smiles atop a cartoon mountain, left hand gripping an astonishingly erect flagpole. Waning male virility, this Orlando, Fla.-based organic medicine company claims, now has an herbal remedy.

Natural Heritage Enterprises (NHE), which makes most of its money on a natural immune system enhancer, introduced the Male Herbal Formula roughly six months ago. Six drops taken three times daily, they say, can boost sexual drive, desire, energy and "the male sense of well-being." Of course, male well-being is in the eye of the beholder; below the FDA's radar, herbal medicine is free to work or not work.

"I first tested it on myself," reports NHE owner Michael Miller, 59. "By the third week, I started noticing a nice, comfortable feeling and I was more easily sexually aroused."

Miller claims friends began to report similar results. "Everybody who ordered it went on to reorder it," he says.

Viagra, an NHE spokeswoman conceded, has its advantages -- the Male Herbal Formula "takes effect a little slower." But at just under 30 cents per day, an herbal tiger in your tank costs significantly less. "The price is right," says the Web page, a mix of crude graphics and earnest appeals to common sense. "Hey, we are a small company. We have to make a great product!"

NHE isn't modest with its recipe, either. "Only the finest organic herbs are used," the Web site explains -- "then we use a lot of them." Down the center of the page runs a list of Male Herbal Formula ingredients: yohimbe bark, saw palmetto berries, uva ursi leaves and four kinds of ginseng, to name a few. Indeed, it is yohimbe, extracted from the West African Pausinystalia yohimbe tree, that has recently garnered attention in virility circles. As herbal medicine manufacturers have begun tapping into its alleged aphrodisiac powers, science has taken a look.

According to the February 1 issue of Environmental Nutrition, the active compound in the yohimbe bark increases sexual drive in male rats. While the same results have not been found in humans, recent analysis of seven clinical trials showed the compound to be more effective than a placebo in treating erectile dysfunction. Between one-third and one-half of the men reported some benefit.

Still, the journal article was cautionary. "Yohimbe is not an herb to mess around with. Ironically, [it] is not recommended for men who may seek it most -- older men and those with cardiovascular disease, hypertension and prostate problems. Neither should it be used by those with liver or kidney disease, psychiatric illness or in combination with mood-altering drugs like antidepressants."

Other scientists were less optimistic. "[Yohimbe] has not been proven sufficiently safe or effective," says Varro Tyler, Ph.D, ScD, of the Purdue University School of Pharmacy and Pharmacal Sciences. As for the compounds that include it -- the Male Herbal Formula, for instance -- Tyler reports that none of those tested "had a sufficient amount of the active alkaloid."

Nevertheless, NHE is preparing for major international business. Pfizer itself has taken notice of Miller's little company, insisting that it remove references to Viagra from its Web site. Miller speaks optimistically of the herbal remedy's future -- that hardy mixture of confidence and male well-being.