The aim of our study was to establish the extent to which therapy of hypertrophic obstructive cardiomyopathy (HOCM) can influence the degree of hypertrophy. By means of two-dimensionally guided M-mode echocardiography, 120 patients with HOCM (age range 4-72 years, mean age 41 years) were observed over an average period of 49 +/- 41 months. Depending on the respective therapy, we formed four patient groups: group 1: 13 patients without any therapy (follow-up period 31 +/- 30 months); group 2: 27 patients receiving propranolol (follow-up period 47 +/- 34 months); group 3: 50 patients receiving verapamil (follow-up period 39 +/- 27 months), and group 4: 30 patients with myectomy (follow-up period 34 +/- 32 months). In group 4, as expected, the thickness of the interventricular septum (IVS) decreased postoperatively (from 24.2 +/- 4.5 to 19.8 +/- 6.7 mm, p less than 0.05), and the left ventricular posterior wall (LVPW) thickness also decreased later postoperatively (from 13.0 +/- 2.6 to 11.9 +/- 2.3 mm, p less than 0.05). The left ventricular diameters increased. In groups 2 and 3 treated with pharmacotherapy as in the untreated patients of group 1, on average there was no change in IVS and LVPW thickness nor in the left ventricular diameters (with the exception of increasing left ventricular end-diastolic diameter in the propranolol-treated group). In contrast to group 1, in occasional cases there were substantial decreases of IVS thickness (11% of the patients in group 2, 13% in group 3) or LVPW thickness (13% of the patients in group 2, 12% in group 3).(ABSTRACT TRUNCATED AT 250 WORDS)