1992 � A vague definition of "female sexual dysfunction" (FSD) is included for the first time in an international compendium of diseases used by healthcare systems and doctors around the world.

May 1997 � At the invitation of a leading Pfizer researcher, clinical investigators attend a conference with drug-company executives to discuss research opportunities concerning women�s sexual problems. Nine drug companies pay for the conference.

Sept. 29, 1997 � Pfizer files a new- drug application for its anti-impotence drug Viagra.

March 27, 1998 � The FDA approves the sale of Viagra to treat impotence in men. Within a week, a leading Viagra researcher in Boston tells Time magazine he will give the drug to women, too.

April 1998 � Viagra hits the market. FDA holds an invitation-only meeting of scientists and drug-company executives to draft guidelines for drug research to treat FSD. Industry analysts predict the market for Viagra will more than double if women are added as patients.

June 1998 � Sex researchers devote their annual meeting to discussing how anti-impotence drugs can be tested in women.

October 1998 � Experts hold consensus conference to define FSD. Eight drug companies fund the effort.

February 1999 � Edward Laumann and Raymond Rosen, both Pfizer consultants, publish research indicating that 43 percent of women in a survey experienced "sexual dysfunction" over several months. Research was based on a 1992 survey that asked 1,749 women about their sexual experiences the previous year. The figure is widely quoted in the media and drug industry.

August 1999 � Studies of 17 women indicate Viagra could help women, triggering speculation of a "women's Viagra."

June 2003 � Second impotence conference in Paris includes members of the 1998 group to refine the definition of FSD. Conference organizers order an objective review of the evidence for the first time, and experts conclude little is known about even basic female sexuality.

Feb. 27, 2004 � Pfizer pulls the plug on testing Viagra in women. In giving the drug to 3,000 women, the company found no conclusive evidence that the drug improved their sexual responsiveness. A company news release calls female sexual arousal "a complex constellation of symptoms that are difficult to identify, measure and treat" and says that sexual disorders result "from a broad range of medical and psychological conditions."

Sources: Research by Duff Wilson, Susan Kelleher, Gene Balk