Twenty-seven women with suspected acute pelvic inflammatory disease were studied by laparoscopy and endometrial biopsy. Overall, 67% (18 of 27) of the women had acute salpingitis at laparoscopy, 70% (19 of 27) had plasma cell endometritis, and 67% (10 of 15) had an inflammatory cytologic pattern of the peritoneal fluid. In comparison to laparoscopically detected salpingitis, endometritis detected with biopsy had a sensitivity of 89%, a specificity of 67%, a positive predictive value of 84%, and a false negative rate of 22% in the diagnosis of pelvic inflammatory disease. The corresponding figures for inflammation of the peritoneal fluid were 75%, 67%, 90%, and 25%. This study demonstrates that nonpuerperal endometritis is an entity associated with pelvic inflammatory disease, most likely representing an intermediate stage between cervicitis and salpingitis. Endometrial biopsy as an office procedure is a good alternative to laparoscopy in the diagnosis of acute pelvic inflammatory disease and may in fact detect early cases not yet visible at laparoscopy.