Echocardiographic studies of the pulmonary valve were obtained in 63 adults. Patients with normal pulmonary artery pressure (22 cases) showed an oblique position of the valve images in diastole, slow valve opening slopes (≤ 300 mm/sec), sizable (> 2 mm) posterior displacement of the cusp echoes with atrial systole ('a' dip), and a relatively short right ventricular pre ejection period. In contrast, pulmonary valves in pulmonary hypertension (mean pressure > 20 mm Hg, 41 cases) appeared straight in diastole with rapid opening slopes (> 350 mm/sec) and prolonged pre ejection periods (P < 0.001). In patients maintaining sinus rhythm (25 cases), mild to moderate pulmonary hypertension (mean pressure ≤ 40 mm Hg) was indicated by small 'a' dips (≤ 2 mm), while absence of 'a' dips denoted more severe pulmonary hypertension (mean pressure > 40 mm Hg) when uncomplicated by severe right heart failure. In the latter instance rapid valve opening slopes were associated with large 'a' dips. Echocardiography appears to be of value in the assessment of pulmonary hypertension.