An intraperitoneal inflammatory process has been associated with infertility in women without anatomic distortion of the pelvic viscera, particularly with endometriosis. This phenomenon was investigated by measuring peritoneal fluid (PF) and serum levels of a major secretory product of the macrophage, lysozyme, in fertile and infertile women undergoing laparoscopy. Serum lysozyme levels were in the normal range and did not correlate with total PF lysozyme. Regression analysis revealed a negative correlation between adnexal adhesions and PF volume (P less than 0.05), PF leukocyte number (P less than 0.05), and total PF lysozyme (P less than 0.05). Significant correlations were found between total PF lysozyme and PF volume (r = 0.72, P less than 0.0001) and leukocyte number (r = 0.67, P less than 0.0001). These results suggest that a localized intraperitoneal inflammatory reaction is associated with infertility in the absence of anatomic distortion of the pelvic viscera.