Twelve affected persons in the third decade of life or later, and the 14 nearest age- and sex-matched unaffected relatives, of a large kindred with autosomal dominant hereditary motor and sensory neuropathy not linked to the Duffy blood group (HMSN type IA) were assessed for arrhythmia and cardiomyopathy. Cardiac abnormalities were no more frequent in the affected persons than in the unaffected relatives. The heart of a patient with HMSN type II who had died of complications of cardiomyopathy was found to have rheumatic disease-type myocarditis with Aschoff bodies. The results of this study provide further evidence against an association of cardiomyopathy and HMSN.