During the past eight decades, a large number of studies have examined the possible relationship between blood type and infection. Many publications reflect uncritical attempts to mathematically link unstratified or random data. The interaction of pathogen and erythrocyte membrane may reflect antigenic similarity, adhesion through specific receptors, or modulation of antibody response. Anthropological surveys suggest that the geographic and racial distribution of human blood groups reflects susceptibility of populations with specific blood types to the plague, cholera, smallpox, malaria and other infectious diseases.