During a ten-month period 1,200 U. S. soldiers were admitted to an Army hospital in South Viet Nam with falciparum malaria. Nineteen developed "cerebral malaria," and three of these showed dramatic personality changes manifested as apparent "functional" psychoses. Further evaluation including psychological testing, however, led to the impression that the symptoms had a definite organic basis secondary to cerebral involvement. The authors stress the prognostic implications of differential diagnosis.Abstract Teaser