The three main factors in dental caries--diet, microflora and a susceptible tooth--were identified almost 100 years ago. Since that time a large number of further local and general risk factors have been identified. Diet has long been suspected of contributing towards the caries process but positive proof of its role has been difficult to establish. However, the total consumption of sugar, as well as the frequency of its intake, undoubtedly contributes to the onset of dental caries. Diet is a dominant variable in determining dental caries prevalence and it can mask other factors. Differences of opinion exist as to whether specific micro-organisms are the cause of dental caries. There is, however, substantial evidence to support the key role of mutans streptococci in the process. Among local risk factors are the form and arrangement of teeth, salivary flow and oral hygiene. General risk factors include age, sex, race, geographic location and social class. In fact, the whole social-cultural environment of the community in which the individual lives may have an influence on the development of dental caries.