We developed an ELISA system for the detection of human anti-ovarian antibodies. Bovine corpora lutea were extracted in PBS (pH 7.2) and fractionated by ultracentrifugation. Both the soluble fraction obtained after 80,000 g (S80) and the Triton-extracted membrane fraction (ST288) were used as antigens. Additionally, the luteinizing hormone (LH)/human chorionic gonadotropin (hCG) receptor was isolated by affinity chromatography (wheat germ agglutinin and LH-Sepharose) and also used as an antigen. In 7 of 14 patients with primary sterility and endometriosis a positive reaction was observed. Similarly, 6 of 16 patients with secondary sterility and endometriosis were also positive. Patients being stimulated for in vitro fertilization and presenting either primary or secondary sterility were positive in 5 of 22 and 6 of 16 cases, respectively. In the S80 test 41 of 60 sera presented IgG2 antibodies, whereas in the ST288 test 38 of 60 belonged to the IgG1 subclass. Kappa and lambda chains were equally distributed. Some patients could recognize the unoccupied LH/hCG receptor as an antigen, while others recognized only the complex formed by the hormone plus the hormone receptor. The S80 and ST288 antigens were isolated by affinity chromatography. Gel permeation of the purified antigens revealed in each case the presence of an antigen complex. The apparent molecular weight was between 2,000 and 36,000 D. Cross-reactivity studies using affinity-purified antibodies demonstrated an antigenic relationship of the membrane, soluble, and extractable fractions. NAc-(beta-1----4)-D-glucosaminide and -D-galactopyranoside were the main terminal glycosides.