Abstract We present a study using cross-sectional echocardiography in 39 patients (29 male and 10 female) with discrete subaortic stenosis. Five parameters were evaluated in the study: the morphology of the obstruction, the distance of the stenosis from the aortic valve, the type of insertion, the base of implantation, and any associated anomalies. The lesion could be divided into groups with either fibrous or fibromuscular shelves. In the group of 14 patients with fibrous shelves, the distances from the stenotic lesion to the aortic valve was less than 15% of the length of the left ventricle. The obstructive fibrous tissue was inserted on the septum and extended onto the aortic leaflet of the mitral valve (circumferential lesion) in 12 cases. The base of implantation was narrow in all 14 of them. In the 25 patients having fibromuscular lesions, the distance between obstruction and valve was greater than 18.4% of the length of the left ventricle. The insertion of the obstructive lesion was circumferential in 18 cases and its base of implantation was wide in 20 of the patients. Nineteen patients, 16 of whom had fibromuscular lesions, showed associated anomalies. Statistical analysis showed a good correlation between the type of stenosis and the base of implantation of the stenotic lesion ( P < 0.001) or associated anomalies (< 0.01), but there was no distinction between the groups with regard to the type of insertion (< 0.38). Twenty-five patients underwent surgical correction which was carried out between the ages of 4–14 years. Prosthetic valves (3 aortic and 1 mitral) were inserted in 4 patients. Follow-up investigations were performed in all the patients. Two developed restenosis as a consequence of partial resection of the initial lesion. We conclude that the distance of the stenotic lesion from the aortic valve and the type of associated anomalies are useful features in helping to differentiate the fibrous from the fibromuscular variants of fixed subaortic stenosis.