This account is based on the" first fifty consecutive cases" of fatal P. falci-parum malaria studied at the American Army Institute of Pathology during the recent war. The findings on the whole were similar to those of most other workers, but there were some points upon which new information was obtained. For instance, in the study of the brain lesions, Dr. Spitz found that" plugged" vessels were" not obstructed by parasitized erythrocytes but simply filled and distended by them, as if during life they were part of a moving stream." In cases showing haemorrhage and" granulomas", however, thrombi were found in the" plugged" vessels, including the central arteriole of the" granuloma", and thrombi were occasionally observed in the cortical capillaries. The thrombi were small and often did not completely occlude the lumens of the vessels concerned. The conception of vessels filled, but not obstructed, by parasitized cells is similar to that put forward by Rigdon (1942) in order to explain the apparently reversible nature of the cerebral changes in falciparum malaria. In the kidney, pigmented casts were observed in the distal convoluted lobules in 30 cases and" hemoglobinuric nephrosis", similar to that seen in blackwater fever, was present in seven. In four of the latter cases and in five others, changes were observed in the glomeruli, including" generalized ischaemia, enlargement and increased cellularity." These cases had clinical evidence of azotaemia. The author considers that the incidence of haemoglobinuric nephrosis was unexpectedly high" since there were not other factors except the malaria itself by which to explain this phenomenon." She holds that glomerular dysfunction is an important factor in the pathogenesis of the renal insufficiency observed, and that the nephrosis, together with the myocardial cellular infiltration and adrenal atrophy also observed, provide strong evidence in favour of" circulating toxins or allergens" liberated by P. falciparum. Selective localization of parasites in the various organs could not explain the pathogenesis of the lesions. Thrombosis could be demonstrated only in some of the small cerebral vessels; it was not found in other organs even where, as in the heart," plugging" with parasitized cells was prominent.