The effect of milk on dental caries was studied on a sample of 6-to-11-year-old Italian schoolchildren. The daily amount of milk consumed and the frequency of consumption of sucrose-containing foods were obtained by a 24-hour dietary diary. In the subsequent oral examination, the level of visible plaque and the number of decayed, extracted and filled teeth (both primary and permanent) of the children were recorded. 439 children (217 boys) who did not use fluoride prophylaxis and with poor oral hygiene were selected from among 890 children. They were divided into three groups according to the frequency of sucrose consumption. The data were statistically analysed using multiple logistic regression. The children consumed a daily average of 209 +/- 133 ml of milk and there were no differences among the three groups in this respect. As expected, the dental health of the children with low sucrose frequency was significantly better than that of the children with high sucrose frequency. The regression on the whole sample showed a weak, significant, negative association between milk consumption and caries (p < 0.05). In the group of high sucrose-consuming children a negative, highly significant association was found (p < 0.001), while in the two groups of low and moderate sucrose-consuming children no association was found. These data suggest that, in the present sample of children who did not use fluoride and with poor oral hygiene, milk has a caries preventive effect only on those subjects with a high daily sucrose-consuming frequency.