Surgery and cardiac pacing are the two main non-drug treatments for hypertrophic cardiomyopathy. Various surgical techniques have been proposed over the last 35 years: myotomy, myotomy-septal myomectomy, isolated mitral valve replacement, heart transplantation. Patients eligible for surgery are those with severe symptoms (NYHA stage III or IV) and refractory or no longer responding to drug treatment. The choice between the various techniques is based on morphological and haemodynamic criteria (significant subaortic gradient associated with increased septal thickness, severe and/or organic mitral regurgitation, either isolated or associated with obstruction, or less severe or heterogeneous septal thickness [< 18 mm]) or therapeutic criteria (failure of primary myomectomy, depletion of all surgical possibilities). Analysis of the results of surgery is complicated by the variety of techniques performed and the experience of the various teams. The operative mortality was markedly decreased (between 2 and 11% at the present time); the complications of myomectomy (ventricular septal defect, disturbances of conduction requiring continuous pacing) are still frequent. Intraoperative transoesophageal ultrasonography could help to further decrease the operative risk. Surgery improves functional symptoms and exercise tolerance. This beneficial effect appears to be more marked, more frequent and more lasting than that of medical treatment. Surgical treatment does not ensure permanent cure, as the symptoms related to pathophysiological abnormalities other than intraventricular obstruction (abnormalities of diastolic filling, myocardial ischaemia, arrhythmias) may develop subsequently. No controlled trial has demonstrated a favourable effect on survival. Continuous pacing, introduced more recently, can now be considered to be a therapeutic method in its own right.(ABSTRACT TRUNCATED AT 250 WORDS)