The presence of pneumopericardium following penetrating injuries of the chest is highly suggestive of a cardiac injury. For this reason, it is generally considered that its presence should be an indication for surgery. In the present study 20 patients with pneumopericardium were selected for conservative treatment. All patients were closely observed by means of clinical examination, serial chest roentgenography, electrocardiography, and Doppler echocardiography. In five patients the electrocardiogram showed pericarditis, and in three patients the echocardiogram demonstrated small pericardial effusions. One patient developed tension pneumopericardium 36 hours after admission and required surgical intervention. The remaining 19 patients had an uneventful recovery. We suggest that the presence of a pneumopericardium following penetrating chest trauma is not an absolute indication for surgery. Electrocardiographic and echographic studies may help in the selection of patients for conservative treatment; but the final decision should be made on the basis of clinical signs and symptoms.