The prevalence of dental caries was determined clinically in 2.5-year-old Dutch cleft lip and/or palate children (n = 76) and in children without congenital malformation (n = 75). The parents were given a structured questionnaire regarding the child's dietary habits, oral hygiene, fluoride exposure and social economic background. The prevalence of dental caries was higher in children with oral cleft than in children without oral cleft. Initial caries (white spots) was diagnosed in 17.1% of the subjects with oral cleft compared with 4.0% of the control subjects. Manifest caries (cavities) was found in 26.3% of the children with oral cleft compared with 5.3% of the controls. The dft score (manifest caries) was significantly higher for the oral cleft group (0.59 +/- 1.35) than for the control group (0.11 +/- 0.54). 52% of the total number of initial and manifest lesions were localized to the maxillary incisors. A multivariate analysis yielded initial caries, oral hygiene and treatment with preoperative infant orthopaedics as the variables significantly associated with manifest caries.