Symptoms and signs of decreased cardiac output associated with an elevated venous pressure should alert one to the possibility of delayed cardiac tamponade. Enlargement of the cardiothoracic ratio shown by serial roentgenograms and demonstration of significant pericardial effusion by echocardiogram or radionuclide angiocardiography support the diagnosis. Erratic response of the prothrombin time to administration of warfarin and abnormal results of liver function test are additional clues to its diagnosis. Right heart catheterization documents the presence of tamponade and excludes other diagnostic considerations. Operative decompression of the pericardial space can be accomplished by pericardicentesis, subxiphoid pericardiotomy, median sternotomy, or thoracotomy. Hemodynamic observations following the relief of tamponade assure that an adequate therapeutic procedure has been performed.