A study is reported of sperm autoimmunization in 707 men and its relationship with atherosclerotic coronary artery disease. The following groups were studied: healthy vasectomized men (278), healthy non-vasectomized men (231), vasectomized men with atherosclerotic coronary disease (ACD; 87) and non-vasectomized men with ACD(111). The gelatin agglutination test (GAT), tube slide agglutination test (TSAT) and sperm immobilization test (SIT) were used to detect circulating anti-sperm antibodies. Sperm antibodies developed within 6 months of vasectomy and persisted for more than 20 years. There was no difference in the incidence of antibodies in vasectomized healthy and ACD men. The results of this study provide no evidence for an association between cardiac disease and vasectomy.