An oral health survey was conducted in 1986 on a representative sample of primary school children in Hong Kong. 1483 Chinese children of both sexes, aged 6-12 yr, attending 56 primary schools were surveyed. The DMFT index for the 6-yr-olds was 0.1, and for the 12-yr-olds it was 1.5. Forty percent of the 12-yr-olds were clinically caries-free. The permanent molars constituted 90% of the total caries experience of the 12-yr-olds. Over 90% of the caries lesions were found in pits and fissures. The dental caries treatment need in the permanent dentition was low and of the simple type. A great reduction in the dental caries experience of the permanent dentition of children has occurred since the introduction of water fluoridation 25 yr ago. In addition to treatment care, preventive measures should be provided by the School Dental Care Service for children with a high caries risk.