Acute pericardial diseases are common disorders in several clinical settings. The presentation may include acute pericarditis and its recurrences, incidental pericardial effusion, cardiac tamponade, and occasionally constrictive pericarditis. New diagnostic techniques have improved the sampling and analysis of pericardial fluid and allow a comprehensive diagnostic approach. Deciding on the extent of diagnostic evaluation in the individual patient requires good clinical judgment based on careful evaluation of the risk-benefit ratio of the planned diagnostic and therapeutic options. Most cases of acute pericarditis are viral or idiopathic and self-limited; however, other etiologies should also be considered. The diagnostic yield of extensive laboratory evaluation and pericardiocentesis is low, and invasive procedures should be limited mainly to patients in whom therapeutic intervention is necessary. Treatment should focus on symptomatic relief, usually through the administration of non-steroidal anti-inflammatory drugs, and patients should be carefully evaluated and monitored for common complications of the disease.