Are Advertisers Biased Against Women's Sex Drive?

 For men, problems in the bedroom are now part of an open conversation. Dozens of TV and radio channels offer advice on treating erectile dysfunction and talk about "erections lasting longer than four hours." But advertisers seem squeamish over airing an ad for a female sexual arousal equivalent.

The market for erectile dysfunction drugs is estimated to rake in more than $3 billion a year in the United States. The makers of the "big three" -- Viagra, Cialis and Levitra -- spent over $300 million in advertising alone in 2008, according to Forbes.com. Levitra and Cialis have even scored Super Bowl ad space.

Watch the full story tonight on "Nightline" at 11:35 p.m.

Pfizer, the pharmaceutical company that makes Viagra, boasted on its website that nine of the little blue pills are dispensed every second -- nearly 300 million tablets.

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