A survey of bacterial pericarditis in children at Charity Hospital shows an increasing preponderance of staphylococcal infections. It is impressively less common as a complication of pneumonia and osteomyelitis than it was two decades ago. The site of entry for organisms is usually difficult to determine, but the pericarditis is always part of a generalized infection. In a minority of the patients it is the outstanding therapeutic problem. Though the child may be critically ill with a poor prognosis, the outlook is better than it was in preantibiotic days. Treatment should be influenced by careful evaluation of sensitivity of the causative organism to various antibiotics; open pericardial drainage may be necessary if the clinical response is poor. Earlier diagnosis may improve the outlook, and this will depend on a high degree of suspicion. Other factors seem less important in prognosis. Constrictive pericarditis will probably not be a problem if recovery from the acute stage occurs.