We have studied the echocardiographic and phonocardiographic findings in 18 patients with obstruction to ventricular outflow at subpulmonary valve level. The aetiology was congenital in 13 patients, a result of hypertrophic cardiomyopathy in three, and infiltration of the right ventricular outflow tract by glycogen or lymphoma in the remaining two. Abnormal systolic motion of the pulmonary valve, fluttering, and early or midsystolic closure were seen in 16 of 17 patients in whom the cusps were visualised. Normal pulmonary valve motion was found in one patient with coexisting pulmonary valve stenosis. In congenital infundibular stenosis the delay of the pulmonary component of the second heart sound (P2) was related to the severity of the obstruction. A pulmonary ejection sound, defined as a high-frequency sound occurring at the moment of full pulmonary valve opening, was absent except in the patient with coexisting pulmonary valve stenosis. In hypertrophic cardiomyopathy with obstruction to the right ventricular outflow, the ejection systolic murmur was softer with inspiration, a finding that contrasts with the respiratory variation seen with fixed obstruction. Recognition of these abnormalities should allow an accurate non-invasive diagnosis to be made and permit assessment of severity when P2 can be recorded.