The radiological studies are very important in the diagnosis of pericarditis. The clinical and radiological findings of 57 cases of pericarditis which were diagnosed at the Seoul National University Hospital during past seven years from January 1969 to November 1976 are analysed. The diagnosis was based on aspiration of the pericardial fluid with or without air replacement, operation such as pericardiotomy or pericardiectomy and other clinical studies. Performed radiological studies include simple chest PA and lateral, fluoroscopy, pneumo-pericardiography, cardiac scan, echocardiography and angiocardiography. The results are as follows: 1. There is no sex difference of incidence and age distribution is even in all age groups. 2. The tuberculous origin is most common and 42.1% of total 57 cases, and pyogenic, malignant, cardiomyopathy, uremia and trauma are the etiology in decreasing order. The idiopathic pericarditis are 11 cases. 3. The main symptoms were dyspnea(61.4%), ches pain(14.0%), abdominal distension(14.0%) and the physical findings of pericarditis were remote heart sound(59.6%), hepatomegaly(59.6%) and neck vein engorgement(49.1%). 4. Pericardiocentesis was performed in 37 cases and the nature of the effusion was bloody in 51.4%, seroexudate in 29.7% and us in 18.9%. 5. Cardinal findings of pericardial effusion in simple chest PA were cardiomegaly(80.7%), acute cardiophrenic angles(68.4%), pleural effusion(56.1%) and straightening of left cardiac border or narrowing of cardiac waist(49.1%). 6. On the pneumopericardiography, the thickness of the pericardium is not related to the etiology but to the duration of the diseases.