For patients enrolled in the Coronary Artery Surgery Study (CASS), surgery was recommended for 46.5 per cent of Blacks and 59.4 per cent of Whites, despite similar clinical and angiographic characteristics. Of those recommended, 80.5 per cent of Blacks and 90.4 per cent of Whites had bypass surgery. These differences were most apparent for Black laborers. Overall, only 38.0 per cent of Blacks had coronary artery bypass surgery, whereas 58.4 per cent of Whites received surgery.