A 2½-year-old boy was referred to the Children's Hospital of Pittsburgh with a history of wheezing, mild fever for two weeks, and abnormal chest roentgenographic findings. He had been in relatively good health, but from age 4 months he had had several episodes of wheezing that improved and resolved with bronchodilator therapy. On admission, the boy was febrile, tachypneic, and wheezing loudly. The right side of his thorax was bulging, and decreased breath sounds were present over his right lung. He had a leukocyte count of 16× 109/L (16000/mm3), a hemoglobin value of 111 g/L (11.1 g/dL), and a hematocrit value of 0.34 (34%). His serum electrolyte levels and urinalysis findings were normal. Anteroposterior and lateral roentgenograms of the thorax were obtained (Figs 1 and 2). A drainage tube was inserted in the right side of the thorax from which 920 mL of purulent material was