Starting in 1969, periodic cross-sectional examinations of schoolchildren have been carried out in the city of The Hague. In 1989 the periodic examinations were continued and, in general, caries prevalence was found to be very low; D3MFS values ranged between 1.5 and 2.2 at age 11.8 years. Compared to 1984, 5-year-old-children of low and medium socio-economic levels (SES) in 1989 had significantly higher d3mfs values (p less than 0.01), mainly due to a marked increase in decayed surfaces per child; a significant increase in caries experience of the deciduous dentition amongst 7-year-olds of low social level was found (p less than 0.01). A further reduction of D3MFS values for 7-year-old children of low and medium SES could be observed in 1989 compared to 1984. Between 1978 and 1989 a marked D3MFS reductions amongst 11-year-olds in the three social levels was found. Possible explanations for the observed differences in caries experience between 1984 and 1989 are discussed.