It is commonly believed that autoimmune or isoimmune responses to human sperm antigens are associated with human infertility. We examined an enzyme linked immunosorbent assay (ELISA) kit used in the detection of antisperm antibodies in the sera of women with unexplained infertility. 1) For the ELISA assay, an absorbance at 405nm greater than 0.300 was considered positive. Of the 83 sera of infertile women studied, 20(24.1%) were positive. This value was significantly higher than that of the control group: 10% of pregnant women, 11.1% of unmarried women and 10% of healthy men (p less than 0.05). 2) The results obtained with ELISA were compared with those of the sperm immobilization test. Comparison of the results of ELISA with those of the sperm immobilization test indicated that these methods detect a different, though often overlapping, spectrum of antibody activity. 3) The results obtained with ELISA did not always correlate with those of the Huhner test. However the ELISA method may be useful in the clinical screening of antisperm antibodies because of its simplicity and rapidity.