The epidemiology of 478 cases of schizophrenia, acute psychosis, and manic-depressive psychosis was examined in Papua New Guinea for the years 1970 through 1973. Factors such as bias, referral habits of doctors, community tolerance, disease, accessibility to medical care, and migration are discussed as possible explanations for the sharply different patterns of prevalence of schizophrenia in certain areas of the country. The authors conclude, however, that these factors are not sufficient to explain the differences and that concomitants of Western civilization such as certain viruses must also be considered as possible etiological agents.Abstract Teaser