Clinical and laboratory results and pathological findings are presented for 12 cases of acute pulmonary insufficiency due to falciparum malaria. Renal and cerebral complications were also seen in all cases. Hematologic studies indicate disseminated intravascular coagulation in all cases, and hemorrhagic diathesis was noted in ten cases. Nine patients died, and intracapillary fibrin clots were seen in internal organs in 2 of 8 postmortems. Disseminated intravascular coagulation is probably an important mechanism causing serious complications, particularly acute pulmonary insufficiency. A high degree of parasitemia, massive intravascular hemolysis, and delay in recognition and treatment of disseminated intravascular coagulation are important in the outcome. The survival of three cases is believed to be the highest reported survival rate of this lethal complication.