To estimate the prevalence and main causes of infertility, a multicentre survey was conducted over 1 year (July 1988-June 1989) in three regions of France. All the 1686 couples in these regions, who consulted a practitioner for primary or secondary infertility during this period, were included in the investigation. The prevalence rate of infertility was found to be 14.1%, indicating that one woman out of seven in France will consult a doctor for an infertility problem during her reproductive life. The main causes of female infertility were ovulation disorders (32%) and tubal damage (26%), and of male infertility oligo-terato-asthenozoospermia (21%), asthenozoospermia (17%), teratozoospermia (10%) and azoospermia (9%). Infertility was also found to be caused by disorders in both the male and female partners together; thus in 39% of cases both the man and woman presented with disorders. The woman alone was responsible for infertility in one-third of cases and the man alone in one-fifth. Unexplained infertility was found in 8% of the couples surveyed.