During a 30 mo. period, 229 couples were evaluated for infertility at the Naval Regional Medical Center, Oakland [California, USA]. Laparoscopy was used in all cases of otherwise unexplained infertility. The resulting laparoscopic examination of the female partner of 24 such couples demonstrated abnormal findings in 18 (75%). Of these 18 subjects, unsuspected endometriosis was found in 11 (46%) and peritubal adhesions in 7 (29%). Of the 229 couples evaluated, only 8 (3.5%) failed to show some etiologic factor associated with infertility. The previously reported 10-20% incidence of unexplained infertility is too high an estimate in view of the additional information made available through pelvic endoscopy.