The goal of surgical treatment in hypertrophic obstructive cardiomyopathy is the elimination of the obstruction in the left ventricular outflow tract. 64 operations were performed in 63 patients with HOCM and there was 1 perioperative death. All patients, except 5, were symptomatically improved; the extent of symptomatic improvement was positively related to the completeness of relief of the subvalvular stenosis. During the first 5 years after the operation, 20% of the patients experienced reappearance of symptoms, during later follow-up symptomatic deterioration seemed to occur at an even higher rate. Preoperative left and right heart failure was improved in 3 out of 5 patients; this complication occurred in 4 other patients during the late postoperative follow-up. Congestive heart failure was the cause of late death in 5 patients, 3 died suddenly and 1 each of myocardial infarction or arrhythmia. The 15-years, actuarial survival rate is 63% corresponding to the total yearly mortality of 2.6%. The operation improves symptoms, hemodynamics and some of the complications of HOCM. However, surgery does not cure the disease, and it cannot be decided yet whether or not it slows down the progression of this condition. Transventricular and combined transventricular and transaortic myectomy was more efficient for relieving the subaortic stenosis than the purely transaortic approach. A-V block was more frequent after the transventricular approach, and aortic incompetence occurred more often after transaortic myectomy; these complications did not increase the postoperative mortality. A clear effect of the different surgical methods on the long-term results cannot yet be established. Operative indications are reviewed in the light of the presented experiences.