Geographic effects on caries prevalence have been noted in studies in the United States, Australia and South Africa. Australia, because of its large land mass, is a useful standpoint from which to gauge such effects, particularly since countrywide data from the School Dental Service is processed centrally, and since the Australian Bureau of Statistics has recently conducted a nationwide survey of adult dental health status. Both studies reveal a distinct impact of geographical factors on dental morbidity. DMF scores in 12-yr-old children are higher in the southern states, and rates of edentulousness in 35-44-yr-olds in Tasmania (latitude 40(0)-45(0)S) are double those for the more northerly states.