A prospective, four-year longitudinal study of 209 Peruvian children was conducted to evaluate the effect of a single malnutrition episode occurring at infancy (i.e., < 1 year of age) on dental caries in the primary teeth. Children were recruited into the study at age 6-11 months after they had suffered from a malnutrition episode and were thus classified by anthropometry as either: (1) Normal; (2) Wasted (low weight for height); (3) Stunted (low height for age); or (4) Stunted and Wasted (S and W). Eruption of the primary teeth was significantly delayed in all malnourished children; however, the effect of stunting--that is, retarded linear growth--was more pronounced and lasted longer than that of wasting or acute malnutrition (i.e., 2.5 vs. 1.5 years, respectively). By age 4 years, children from group 4 (S and W) showed a significantly higher caries experience in the primary teeth than did those in any of the other three groups. In summary, this longitudinal study has confirmed previous studies in animals and indirect epidemiological evidence which had suggested a cause-effect relationship between early malnutrition and increased dental caries.