An unusually prolonged case of heparin-induced severe thrombocytopenia and decompensated disseminated intravascular coagulation (DIC) is described. The patient, treated with heparin at a dosage of 25,000 units/day for 3 days and 12,500 units/day for an additional 4 days because of a clinically suspected deep venous thrombosis, developed (4 days after the discontinuation of heparin) a clinical and laboratory picture of severe DIC, manifested by subcutaneous hematomas and ecchymoses. Platelet count was 24 x 10(9)/l, fibrinogen level 89 mg/dl and fibrin-degradation products between 3,200 to 6,400 ng/ml. A thorough laboratory and instrumental evaluation failed to demonstrate any underlying disorder. No heparin-dependent aggregating factor was detected in the serum of the patient. The patient recovered spontaneously. Whereas fibrinogen and fibrin-degradation products reverted to normality within four weeks, platelet count normalization was delayed until the sixth week after heparin discontinuation.