B lood cysts of the heart valves are frequently seen as a postmortem finding on the atrioventricular valves of infants aged 16 months. They are usually small, rounded, pinpoint to pinhead nodules on the submarginal part of the atrial surface of the CUSPS,~,~ but are also seen less often on the ventricular surfaces of the semilunar valves2 Although these cysts seem to disappear after 6 months of age, rare cases have been described in children and adults.M We describe a child who underwent successful1 surgical excision of a blood cyst from the pulmonary valve. A lo-year-old girl was referred because of suspected pulmonary stenosis. At the age of 8 years, a precordial murmur was observed. There were no symptoms of cardiac dysfunction. She looked healthy. Physical examination was normal except for the heart. There was a palpable systolic thrill, and palpable pulmonary valve closure in the second left intercostal space. An opening click of the pulmonary valve and a grade 3 to 416 systolic ejection murmur was heard at the same area. A pulmonic second sound was accentuated ana’ relativelyhed splitting was established. The electrocardiogram showed a frontal QRS axis of loo”, and a mild right ventricular hypertrophy. Posteroanterior x-ray projection demonstrated moderate prominence of the pulmonary trunk. Two-dimensional echocardiography revealed an abrupt pressure gradient between the pulmonary artery and right ventricle of 68 mm Hg. Cardiac catheterization confirmed the diagnosis. Pulmonary balloon valvuloplasty reduced the gradient to 41 mm Hg. On the cineangiogram, there was a persistent, rounded, sharply demarcated filling defect in the pulmonary trunk, slightly below the valve (Figure 1). The cineangiocardiogram also showed mild pulmonary stenosis and poststenotic dilatation of the main pulmonary artery. On June 17, 1992, open heart surgery was peformed. At operation, the pulmonary artery was seen to be greatly dilated ana! a systolic thrill was palpated over the pulmonary trunk. A longitudinal incision was made and a dark red-colored, lobulated cystic mass measuring I .5 X 1 X 0.8 cm was seen (Figure 2). The valve cusps were normal. The cyst originated from the left posterior pulmonary valve leaflet. The cyst was removed by sharp dissection at its base. During the excision the cyst was opened and bloody fluid flowed out. The basilar layer of the cyst at its base was not removed from the ventricular suface of the cusp. The excised cyst was ovoid and lobulated, and measured I .5 X 1 X 0.9 cm. The wall of the cyst was 0.1 to 0.2 cm in thickness, and lined with a single layer of cuboidal cells overlying an eosinophilic, relatively hypocellular stroma. After operation, no murmur was heard, and on subsequent examination no gradient