A retrospective analysis of 133 patients was performed to define the factors identifying those individuals at risk for the more serious causes of pericardial disease. In 90% of the cases, the initial assessment from data obtained without pericardiocentesis or pericardiectomy proved correct. Underlying tuberculous or maligant pericarditis were the most common sources of error on initial assessment. Hemodynamic compromise exclusive of anticoagulants, roentgenographic cardiomegaly, pleural effusion, low voltage on ECG, and large pericardial effusion by echocardiography were more common (P less than .05) in tuberculous pericarditis than in acute idiopathic pericarditis. We discuss similar risk factors in patients with chronic idiopathic, rheumatologic, and uremic pericarditis. Anterior pericardiectomy is favored as the diagnostic procedure of choice in patients at risk for the more serious causes of pericarditis because of greater safety, diagnostic sensitivity, and potential therapeutic benefit.