The World Health Organization sponsored a multicenter, collaborative investigation of the infertile couple by use of a standardized approach. The study was conducted between 1979 and 1984 in 33 centers in 25 countries throughout the developed and developing world. More than 5800 couples completed the investigation. Bilateral tubal occlusion and other infectious infertility etiologies were clearly related to a woman's history of sexually transmitted disease, pelvic inflammatory disease, and pregnancy complications. African centers had the highest rates of infectious infertility, more than threefold that in other regions. The relative contribution of either abortion or childbirth to these infectious causes apparently differed among the four regions investigated. Public health programs aimed at reducing these infections may pay reproductive health dividends.