Sperm-bound immunoglobulins were found in 27 (32%) of 84 infertile men with palpable varicoceles. These men were divided into two groups based on the presence (group I; 32%) or absence (group II; 68%) of sperm-bound immunoglobulins, as measured by an enzyme-linked immunosorbent assay. Circulating antisperm antibodies were identified in 52% of patients with sperm-bound immunoglobulins and 14% of group II patients. The presence of sperm-bound immunoglobulins was associated with a small but significant decrease in both sperm concentration and motility. Sperm-bound immunoglobulins are present in a greater percentage of infertile men with varicoceles than infertile men without varicoceles. Their presence may be a marker for damage to the seminiferous epithelia in men with varicoceles and may also contribute to varicocele-associated infertility.