In an attempt to better understand congenital subaortic stenosis, we reviewed 19 consecutive pediatric patients undergoing surgery for this problem between 1973 and 1984. Preoperative cardiac catheterization demonstrated subvalvular stenosis in all patients and associated anomalies in 11 patients. All patients underwent transaortic resection of the subaortic membrane. Five patients underwent concurrent additional cardiac procedures. An 8-month-old infant with multiple cardiac anomalies was the only operative mortality. Follow-up extended to 16 years, with a mean of 6.9 years. In five symptomatic patients, cardiac catheterization revealed a mean systolic pressure gradient of 33.0 +/- 31.94 mm Hg 24.7 months (mean) after surgery. Two of these patients (11.1 percent of survivors) required reoperation. Twelve of the remaining 13 asymptomatic patients underwent echocardiographic follow-up, and 4 were found to have recurrent stenosis with 1 requiring surgery (5.6 percent of survivors). Our experience shows that transaortic resection of the subaortic membrane is an acceptable treatment for subvalvular aortic stenosis, but is associated with a high incidence of recurrence requiring reoperation (3 of 18 or 16.7 percent). Consequently, it is reasonable to consider the role of alternative therapies which may help prevent recurrence in selected cases.