Subvalvar aortic stenosis can be associated with progressive left ventricular outflow tract obstruction, aortic insufficiency, and infective endocarditis. We reviewed the records of 36 surgical patients who underwent 39 operations for subaortic stenosis. Seventeen patients had associated congenital cardiac anomalies. One perioperative death occurred in a patient with tetralogy of Fallot. The mean preoperative left ventricular outflow tract systolic pressure gradient was 64 +/- 5 mm Hg (+/- standard error of the mean) and decreased to 9 +/- 2 mm Hg postoperatively (p less than 0.001). Reliable preoperative and postoperative information regarding aortic valve function was available for 27 patients. Aortic insufficiency was found in 17 (63%) of those patients preoperatively. Postoperatively, insufficiency increased in 3 patients and decreased in 4; none of these changes was major. Severity of preoperative aortic insufficiency increased significantly with age (p less than 0.05), but did not correlate with left ventricular outflow tract gradient. The information from this study and previous studies suggests that resection of subaortic stenosis is safe and effective, and operation at the time of diagnosis, regardless of left ventricular outflow tract gradient or symptomatic status, is a reasonable therapeutic alternative.