Pericardioscopy is a new diagnostic tool for macroscopic visualization of alterations in both the epicardium and pericardium. We report on 35 patients with pericardial effusion due to inflammatory perimyocardial disease. After puncture of the pericardial effusion, an 8F sheath was introduced over a guidewire under X-ray control. The pericardial pressures were measured; the fluid was removed by aspiration and exchanged with 100 ml of body-warm saline until the pericardial fluid was clear. To visualize the peri- and epicardium, for video- and photo documentation, two sorts of 8F endoscope were used, either a flexible fibreglass version or a rigid 110 degree one--both made by Storz. Cytology of the fluid and optically guided and controlled epicardial and pericardial biopsies were performed to classify the form of pericarditis. A specific diagnosis of viral pericarditis could thus be established in seven cases--by in situ hybridization for cytomegalovirus (n = 3) and by microneutralization test for enteroviruses and/or coxsackievirus B4 isolation (n = 4); of lymphocytic perimyocarditis in 16; of bacterial pericarditis in seven and antibody-mediated autoreactive pericarditis in five cases.