We describe a familial cardiomyopathy affecting three generations of family members with similar electrocardiographic abnormalities and human leukocyte antigen (HLA) haplotype. Autopsy findings in two of our patients were diagnostic of hypertrophic cardiomyopathy, although surviving affected members do not show ventricular hypertrophy on echocardiography. One patient's echocardiogram revealed giant atria in the absence of ventricular hypertrophy, suggesting a restrictive form of cardiomyopathy. In this kindred, an HLA haplotype appearing in affected, but not in healthy, family members may predict occurrence of disease during its presymptomatic phase in subsequent generations.