Pericardioscopy is a new diagnostic tool to visualize macroscopically alterations of both the epicardium and pericardium. For the first time the macropathology of the epicarditis and pericarditis can be observed in vivo by the cardiologist in viral, bacterial, uremic and autoimmune cardiac processes. It enables us also to get an insight into neoplastic and metastatic processes affecting the heart and the pericardium. The prerequisite is the documentation of a larger pericardial (greater than 150 ml by the cubic model) effusion with an echocardiographically documented effusion of type C (Figure 1b), which must have at least 5 mm separation of the epicardial and pericardial layer in diastole at the anterior side of the heart when echocardiographic imaging is performed from the subxyphoidal or third intercostal space (Figure 1a). The first experience in 30 patients is reported. After puncture of the pericardial effusion a 9F sheath was introduced by use of a guide wire under echocardiographic and/or x-ray control (Figure 3). The fluid was removed by aspiration and 100 to 150 ml of body warm saline were infused in the pericardial sack. A flexible 8F fiber glass instrument (Vantec, Baxter or Storz) and a rigid 110 degrees 8F endoscope (Storz) were used for visualization of peri- and epicardium and for video documentation (Figure 2). After endoscopic inspection of the macropathology fibrinous strands (Figure 4) or increased vascular injection (Figure 5) can be observed in viral, autoimmune or idiopathic pericarditis or perimyocarditis. In the latter three forms of pericardial effusion only inflammatory cells (Figure 6) can be observed when the pericardial fluid is analyzed.(ABSTRACT TRUNCATED AT 250 WORDS)