HLA tissue typing was performed in 43 unrelated white persons with hypertrophic cardiomyopathy (HCM) living in the northern part of Belgium. The frequency distribution of the 14-HLA-A, 18 HLA-B, 5 HLA-C and 10 HLA-D antigens, which were tested, was similar in patients with obstructive, provocable obstructive or non-obstructive HCM to that of a control group of 800 normal persons.