In order to detect peritoneal abnormalities that could account for infertility associated with endometriosis, 122 infertile individuals were studied at the time of laparoscopy for diagnostic purposes or for in vitro fertilization. Four groups were defined: group 1, laparoscopy without endometriosis; group 2, laparoscopy with endometriosis; group 3, in vitro fertilization without endometriosis; and group 4, in vitro fertilization with endometriosis. Mean peritoneal fluid volume was greater, although not significantly so, in group 4 (29.0 +/- 6.6 ml, mean +/- SEM) than in group 3 (18.2 +/- 2 ml). The concentration and total number of pelvic macrophages were similar for groups 1 and 2. The total number of pelvic macrophages was increased in group 4 (16.9 +/- 4.2 x 10(6)) versus group 3 (10.0 +/- 1.8 x 10(6)) (p = 0.08). The mean sperm phagocytosis in vitro did not differ among the four groups studied. Interleukin 1 activity within the peritoneal fluid and the in vitro interleukin 1 production rate did not differ between individuals with and without endometriosis. Peritoneal fluid and macrophage supernatants from individuals with endometriosis were not embryotoxic when studied in an in vitro mouse embryo system.