W ell before sildenafil (Viagra), people relied on aphrodisiacs to increase sexual desire... boost stamina... improve performance... and increase pleasure.

Many of these compounds owe their reputation to folklore, but several herbs and dietary supplements have proven sex-enhancing effects.

Good news: Products that improve sex naturally may be less likely to cause serious side effects than prescription drugs. Many strengthen the cardiovascular system and help regulate hormone production. That's as important for good sex as having an erection or being sufficiently lubricated.

Unlike sildenafil, sex-enhancing herbs and supplements aren't taken just an hour or so before sex. They're taken daily until there's a noticeable improvement in sexual performance.

At that point, some people take a pause to see if the herbs and supplements are no longer necessary. Others continue taking the preparations indefinitely.

Important: Use herbs and supplements only under medical supervision. That way you'll be sure to get the product and dosage that's right for you.

Caution: Fresh or dried herbs differ greatly in potency from batch to batch. Use capsules or tinctures, instead. They've been standardized to contain the proper amounts of active ingredients.

For better sex, try one of the following natural enhancers. Select the one that best suits your needs. Give each preparation a few months to work. If you see no effect, try another.

GINKGO BILOBA

Ginkgo contains a variety of compounds that relax blood vessels and increase circulation to the brain and pelvic area.

For women, increased blood flow improves vaginal lubrication and sexual responsiveness.

For men, adequate blood flow is essential to achieve and sustain erections.

Typical dosage: Capsules: 40 mg to 60 mg of 24% standardized powdered extract three to four times daily. Tincture: 30 drops three to four times daily.

Side effects: Ginkgo may cause dizziness, headache or heart palpitations.

Caution: Ginkgo is a blood thinner and can increase the blood-thinning effects of aspirin and warfarin (Coumadin). Check with your physician before using ginkgo if you're taking either medication.

MUIRA PUAMA

Also known as "potency wood," this herb contains sterols and other compounds that boost levels of testosterone, a hormone that plays a critical role in sexual desire in women as well as men.

Muira puama also contains volatile oils, including camphor and beta-carophyllene. They're thought to restore sex drive by stimulating nerves in the brain's pleasure center.

Typical dosage: 250 mg three times daily in capsule form.

Side effect: Muira puama may lower blood pressure by as much as 10%. Check with your doctor before using this herb if you have low blood pressure (hypotension).

GINSENG

This herb is an "adaptogen," meaning it helps the body compensate for extended periods of stress. Stress can cause sexual desire and performance to plummet.

Compounds in ginseng root stimulate the adrenal glands to release substances that lower the levels of adrenaline and other stress hormones.

These compounds also improve blood flow to the penis, help tissues use oxygen more efficiently and boost production of testosterone in men and progesterone in women.

Typical dosage: Capsules: 10 mg to 50 mg one to three times daily. Tincture: 30 to 60 drops daily.

Side effect: Ginseng may cause diarrhea... high blood pressure... sleeplessness.

ASHWAGANDA

A member of the pepper family, this herb contains withanolides, substances that increase the activity of testosterone and progesterone. Ashwaganda also relieves stress and anxiety.

Typical dosage: Capsules: 1,000 mg once or twice daily. Tincture: 60 to 90 drops two or three times daily.

Side effects: Because ashwaganda has anti-anxiety properties, it should not be used by anyone taking medications to treat anxiety and/or depression. The herb could intensify the drugs' actions as well as their side effects. Ashwaganda may also trigger miscarriages.

ARGININE

Taken in supplement form, this amino acid has been shown to relax smooth muscle contractions. This boosts arterial dilation, bringing more blood to the pelvic area.

The body uses arginine to produce nitric oxide, a chemical needed to achieve erections. (Sildenafil works in part by making nitric oxide more readily available in the body.)

Typical dosage: 1,000 mg to 2,000 mg twice daily in capsule form. Take capsules between meals, since many foods contain lysine, an amino acid that counteracts arginine's effects.

Side effect: Don't take this herb if you get cold sores caused by the herpes simplex virus. Arginine stimulates viral replication.

FOR MEN ONLY

The herb yohimbe is approved by the FDA for treating impotence and low sex drive.

Yohimbe contains a compound called yohimbine, which helps dilate blood vessels in the penis. Most men who take yohimbe experience an increase in sexual desire within an hour.

Typical dosage: 15 mg to 25 mg daily in capsule form. Divide into several doses throughout the day to minimize side effects. Take smaller amounts at first -- for example, 5 mg or 10 mg a day -- then gradually the amount over weeks.

Side effects: Elevated blood pressure, nausea, heart and anxiety. Use yohimbe only under medical supervision.

FOR WOMEN ONLY

The herb dong quai contains plant sterols that help correct estrogen deficiencies.

Studies suggest that dong quai can increase sexual desire as well as the intensity of orgasms.

Typical dosage: Capsules: 1,000 mg three to four times daily. Tincture: 45 to 60 drops two or three times daily.

Caution: Pregnant and lactating women should not use dong quai. The herb also increases sensitivity to sunlight.