A complete clinical study was performed for 364 patients with hypertrophic obstructive cardiomyopathy who were operated on in the years 1963 to 1991 (217 male, 146 female, mean age 40 years, range 5 months to 76 years). Transaortic subvalvular myectomy was performed in 272 patients (hospital mortality 2.9%), and 92 patients needed additional cardiac procedures simultaneously (hospital mortality 10.9%). A complete follow-up study (100%) included 346 patients who survived the operation. The shortest follow-up time was 2 months and the longest 25.2 years (mean 8.2 years). Most of the patients improved clinically by one to three classes (New York Heart Association). During the observation period 38 patients (10.4%) died. The death of 17 patients was closely related to the original disease (4.9%). Other causes, unrelated to hypertrophic obstructive cardiomyopathy, were responsible for the death of 21 patients (5.8%). In consideration of these data, the yearly total death rate was 2.2%; in close relation to hypertrophic obstructive cardiomyopathy it was about 0.6%. The cumulative survivals were 88% after 10 years and 72% after 20 years. In our long-term clinical experience it is increasingly evident, despite the restrictions of a retrospective study, that patients with symptomatic hypertrophic obstructive cardiomyopathy and failing medical therapy benefit from transthoracic subvalvular myectomy.