Pericarditis is an inflammatory disorder of the pericardium with or without an associated pericardial effusion. The diagnosis is based on the clinical manifestations and typical ECG changes. Echocardiography is essential to reveal the size of the pericardial effusion and to determine its hemodynamic significance. The precise etiology of pericarditis may be established by pericardiocentesis, pericardioscopy and targeted biopsy and consecutive pericardial fluid and biopsy analysis by molecular biology, cytology, microbiology and immunological techniques. Non steroidal anti-inflammatory drugs and/or colchicine are the mainstay of anti-inflammatory treatment of pericarditis. Systemic corticoid treatment should be restricted to patients with associated autoimmune disorder, relapsing pericarditis and as a complementary therapy in tuberculous pericarditis. In autoreactive pericarditis intrapericardial instillation of triamcinolone is effective with few side effects. In malignant pericarditis the intrapericardial administration of cisplatin prevents early recurrences.