To evaluate the use of MRI in the diagnosis of pericardial disease, 63 patients with pericardial abnormalities or clinically suspected pericardial disease were studied retrospectively. Twenty-three patients had pericardial effusion, 19 patients had pericardial thickening, and 11 patients were referred for evaluation of masses with possible pericardial involvement. The other 10 patients were referred for differentiation of constrictive pericarditis from restrictive cardiomyopathy and eventually were found to have pericardial hematoma or normal pericardium as assessed by MRI. The calculated size of pericardial effusion by MRI showed a good correlation with semiquantitative echocardiographic estimations. MRI could demonstrate fibrinous adhesions in patients with uremic pericarditis. It was also of great value in the differential diagnosis of constrictive pericarditis vs restrictive cardiomyopathy. Pericardial thickness of more than 4 mm was found in patients with constrictive pericarditis. Normal pericardial thickness was demonstrated by MRI in the three patients with restrictive cardiomyopathy. MRI diagnosed hemopericardium correctly as the cause of constrictive symptoms in two patients. Pericardial thickening in patients after cardiac surgery was commonly found by MRI and usually was not associated with clinical signs of constrictive pericarditis. MRI proved to be useful in the diagnosis of pericardial cysts and in the evaluation of paracardiac masses with possible pericardial involvement. MRI is an important technique in the evaluation of the pericardium. It can provide important additional information when diagnosis cannot be made adequately by other noninvasive imaging techniques.