Hypertrophic cardiomyopathy is characterized by unexplained left ventricular hypertrophy. It is uncertain, however, to what extent the right ventricle is also thickened. Right ventricular hypertrophy is found at autopsy in patients who die suddenly but, until recently, systematic evaluation of right ventricular morphology has not been feasible. In this two-dimensional echocardiographic study, a total of 4 to 10 (median 7) right ventricular wall thickness measurements were made from six right ventricular views in 73 patients with hypertrophic cardiomyopathy. Forty-one normal subjects were also studied for comparison. Thirty-two (44%) of the 73 patients had right ventricular hypertrophy with at least two of the wall thickness measurements exceeding 2 standard deviations (SD) from the mean value in the normal subjects. Right ventricular hypertrophy was mild (less than or equal to 8 mm) in 24 patients, moderate (9 to 12 mm) in 7 and severe (greater than 12 mm) in 1. The coefficient of variation of right ventricular wall thickness measurements was similar in normal subjects and patients with and without right ventricular hypertrophy (17 +/- 7, 11 +/- 8 and 10 +/- 8, respectively). The hypertrophy was concentric, with a coefficient of variation of 25% in all but one patient. There was a strong correlation of maximal right and mean left ventricular wall thickness (r = 0.643, P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)