Three patients with coexisting fixed subaortic stenosis and idiopathic hypertrophie subaortic stenosis were diagnosed by cardiac catheterization and cineangiography. Although clinical features inconsistent with a single obstructive lesion were present in 2 cases, in the other case there was no evidence to suggest an associated lesion. After removal of the subvalvular obstruction in 2 patients, postoperative problems developed that were attributed to idiopathic hypertrophic subaortic stenosis. In the first patient the use of isoproterenol and digitalis aggravated hypotension. In the second patient symptomatic idiopathic hypertrophic subaortic stenosis subsequently developed; this was confirmed at repeat catheterization. This lesion was ameliorated by treatment with propranolol. These cases underscore the importance of recognizing coexisting lesions that cause obstruction to left ventricular outflow, both in establishing the correct diagnosis at catheterization and in postoperative care.