Constrictive pericarditis is an uncommon disease, particularly in childhood. Approximately 25 cases have been reported in children below 10 years, the youngest at 2\ m=1/ 2\ years of age.1-12 In approximately twothirds of cases the etiologic agent or mechanism of pericardial constriction is unknown. The interval of time between the original insult to the pericardium and the onset of the constrictive process is rather variable and difficult to determine.2,9 Similarly, the interval of time between the onset of evidence of constriction and surgical therapy or death varies widely.10,13It is the purpose of this report to describe a 7-year-old Negro boy who developed severe constrictive pericarditis within 30 days following an episode of acute pericarditis with effusion. Surgical relief was accomplished 13 days later. The rapid conversion of acute pericarditis with effusion to constrictive pericarditis is unusual.A 7-year-old Negro boy was admitted to the Camden Municipal Hospital on Dec. 23, 1958, with clinical and laboratory findings characteristic of acute meningococcic meningitis. Initial treatment with penicillin and sulfadiazine was followed by some improvement, but fever and toxicity per¬ sisted. On the fifth hospital day a roentgeno¬ gram of the chest revealed fluid at the base of the right lung; a thoracentesis yielded 275 cc. of yellow-colored fluid of high protein content.Marked enlargement of the cardiac silhouette was also observed in addition to fever, abdominal pain and distention, and respiratory distress. On Dec. 29, 1958, muffled heart sounds, a narrowed pulse pressure, hepatomegaly, and electrocardiographic evidence of acute pericarditis were noted (Fig. \A). Because acute cardiac tamponade due to pericardial effusion seemed imminent, the patient was transferred to The Children's Hospital of Philadelphia. The past medical history and fam¬ ily history were noncontributory.Physical Examination.-Examination on entry revealed a 7-year-old Negro boy with a tempera¬ ture of 102 F, pulse rate 120 per minute, respira¬ tory rate 24 per minute, and blood pressure, 100/84 in the arms. Vesicular herpetic lesions were present at the right mucocutaneous junction of the mouth; the neck was supple. There was some flaring of the alae nasi. Distention of the cervical veins was apparent in the erect position. The heart sounds were muffled and no cardiac murmurs were heard. Cardiomegaly was detectable on percussion.Several hours after admission a loud pericardial friction rub was audible. Subcrepitant rales and rhonchi were heard over both lung fields. Dull¬ ness on percussion was noted over the base of the right lung posteriorly. The abdomen was slightly distended, and a large, tender liver was palpable