OBJECTIVES The main objective of this study was to describe the dental health of infants and toddlers with special reference to their dietary habits and oral hygiene behaviour over the first 18 months of life. METHODS The longitudinal dietary data were obtained at 6, 12 and 18 months of age by using a 3-day weighed diet diary. Dental examinations were carried out at 12, and again at 18 months of age. The information on demographic factors and oral hygiene behaviours over the first 18 months of life was gathered by using a structured questionnaire at 12 and 18 months. RESULTS 163 children were studied. Visible dental plaque was present in 18% and 25% of children at 12 and 18 months of age, respectively. No child had dental caries at either 12 or 18 months of age. There was a statistically significant correlation between visible plaque measured as plaque index at 12 months and the mean daily eating/drinking episodes at 6 months (r=0.25, P=0.001) and 12 months (r=0.15, P=0.05). The correlations between plaque index at 18 months and the mean eating/drinking episodes at both 12 months (r=0.2, P=0.04) and 18 months (r=0.2, P=0.02) were low but statistically significant. Nevertheless, there was no significant correlation between accumulation of plaque at either 12 or 18 months and the mean daily frequency consumption of food and drink containing non-milk extrinsic sugars (NMES) at any age. Children who brushed their teeth themselves were more likely to have visible plaque compared with children whose teeth were cleaned by their parents. The partial correlation showed that positive relation between mean daily eating/drinking episodes and plaque was not influenced by tooth brushing.