BACKGROUND Pericarditis is a rare but possibly severe complication of treatment of acute leukemia with cytarabine. METHODS We report a possibly cytarabine-induced acute pericarditis and pleuritis with a rapid onset. A patient with acute myelomonocytic leukemia developed an isolated pericarditis 3 weeks after the first course of chemotherapy with cytarabine and idarubicin. The second course of chemotherapy with cytarabine and amsacrine was started after clinical improvement; 3 days later an acute pericarditis with a large pericardial effusion accompanied by a left pleural effusion developed. A pericardio- and pleuracentesis was performed and the symptoms improved rapidly without reaccumulation of the fluid. The third course of chemotherapy with mitoxantrone and etoposide was completed without further cardiopulmonary complications. CONCLUSIONS The differential diagnosis of pericarditis in the setting of chemotherapy with cytarabine should include cytarabine- induced pericarditis. The pathogenesis remains unclear, directly toxic and immunological mechanisms are suggested. Severe progression with massive pericardial effusion necessitating risky pericardiocentesis can occur and therefore a therapy with high-dose corticosteroids should be considered early.