The course of HOCM is characterized by a slow progression. Symptoms can often be influenced favourably by medical treatment. Altogether there is some difference between the course of untreated and the propranolol-treated patient groups which is, however, not statistically significant. Furthermore, the rate of sudden death is uninfluenced. Comparing clinical and haemodynamic results in medicically treated patients we find a reduction of the outflow tract obstruction in case with clinical improvement but not a reduction of the enddiastolic pressure. Independent on the clinical course there was a significant increase of the enddiastolic pressure after 5.5 years. We may conclude that there is a progredient process of hypertrophy which is uninfluenced by the obstruction and by conservative management. The best results are obtained in the operated group. According to our results a surgical intervention should possibly be considereed more generously.