Though supravalvar aortic stenosis is uncommon and fewer than 80 cases have been described, nevertheless, a clinical picture is gradually emerging based on observations from many different units.This paper is concerned with the diagnosis of supravalvar stenosis in six patients in three generations of a family. The findings are presented to show that supravalvar stenosis may be clinically distinguished from other causes of left ventricular outflow obstruction. CASE REPORTS Case 1. (Fig. 1: 1I.20.) A. McA., aged 23, at the age of 9 had been found to have a basal systolic murmur. Over the next 14 years he was examined at regular intervals and full investigations were undertaken when he began to complain of slight effort dyspnoea and precordial pain on exertion.On examination, he was of normal physique and intelligence. His facial appearance was normal. The only abnormalities detected were in the cardiovascular system.