As part of a nutrition survey, the influence of socio-economic factors on the prevalence and intensity of dental caries was studied in 3,370 Nigerians, 89% of which were under 20 years of age. For comparison, 238 children of Western European origin resident in the major cities in Nigeria were also examined. Mean age-specific df and DF values were extremely low in most of the village communities studied but less so in the Northern Nigerian villages. In most of these underprivileged village groups, the proportion of sample showing one or more decayed teeth varied from 2 to 6%. In contrast to findings in the village societies, educated Nigerians of higher socio-economic background had high prevalence and intensity of dental caries which almost paralleled findings in Western Europeans resident in Nigeria. A similar trend was observed in village children attending boarding schools in the major cities. Village peasants in Nigeria consume diets which are predominantly starchy in nature and grossly inadequate in good quality protein, while in the high socio-economic groups, low-molecular weight carbohydrates account for an increasing proportion of total calorie intake and this occurs largely at the expense of starch. The low caries prevalence among Nigerian peasants inspite of low ingestion of fluoride, poor oral hygiene and universal occurrence of enamel hypoplastic defects is attributed to the fact that starch is a poor substrate for the establishment of plaque and the metabolism of cariogenic organisms.