A sample of 3,347 students between 5 and 14 years of age was selected from the entire student population in the province of Granada (Spain) to study the prevalence of dental caries and several risk factors for the disease. Decay was ascertained in the study population by means of the following indices: df, DMF, and DMFS. Risk factors considered were the level of oral hygiene, number of between-meal sugar-containing food, and flouride concentration in drinking water. The indices mentioned showed a clear relationship to the age of the participants in the study. The level of oral hygiene did not show a clear association with dental caries measured through the df and DMF indices. Curiously, a higher correlation was noted between the disease in deciduous teeth and fluoride concentration than between the disease in permanent teeth and the latter factor.