In order to confirm the recent observations of the particular incidence of some HLA antigens in the familial hypertrophic cardiomyopathy we have determined the HLA-A, B and C antigens in the components of a family with high prevalence of hypertrophic cardiomyopathy (10 males and 7 females, age from 10 to 75 years). Six patients were affected by the disease. In one case (sudden death) the diagnosis was established by necroscopy; in the other living subjects by the characteristic echocardiographic features after having ruled out the conditions which can result in secondary myocardial hypertrophy. HLA typing showed the A9, Bw35, Cw4 aplotype in 4 of the 5 living patients affected by hypertrophic cardiomyopathy (2 with obstruction). This aplotype however was not shared by the other patient and was found in one healthy member of the family. Two patients affected by hypertrophic cardiomyopathy without obstruction did not share any aplotype while the 2 subjects with obstructive hypertrophic cardiomyopathy had the same aplotype of a healthy member of the family. Accordingly the genetic study of this family does not allow to establish a steady correlation between hypertrophic cardiomyopathy and HLA aplotypes.