Between January 1973 and December 1993, 66 patients underwent surgery in our department for hypertrophic obstructive cardiomyopathy; mean basal outflow gradient was 48.4 +/- 36 mmHg, 20 patients had mitral valve lesions. Thirty six patients underwent myotomy-myomectomy alone, 13 mitral valve replacement alone, and 17 both myotomy-myomectomy and mitral valve replacement. The 30-day mortality rate was 7.5% for all patients; predominant risk factors were gender (female), greater cardiothoracic ratio, preoperative episodes of atrial fibrillation and lack of syncope. Overall survival rate (operative mortality included) was 65.3 +/- 8.6% at 13 years. Predominant risk factors for late mortality were the same than above, plus mitral valve replacement; so mitral valve repair, whenever feasible should be undertaken. Forty nine patients are still followed up: 46 are asymptomatic; Doppler mean basal outflow gradient was reduced to 10 +/- 1.4 mmHg. In conclusion, surgery relieves symptoms and outflow obstruction, and allows mitral valve reconstruction.