In 1973, 1976, 1979, 1982 and 1988 caries investigations were carried out amongst 6- and 12-year-old primary schoolchildren to study the effectiveness of a dental health campaign begun in 1973. This campaign and the school dental health services were stopped in 1985. In all the years, except 1988, radiographs formed part of the caries examination. The percentage of 6-year olds with a caries-free dentition increased from 4 per cent in 1973 to 47 per cent in 1988, and for 12-year olds from 0 per cent in 1973 to 45 per cent in 1988. The mean dmfs score decreased steeply from 14.4 in 1973 to 3.8 in 1982 and rose slightly to 4.0 in 1988. This latter score was 4.6 if a correction for the X-ray effect were applied. The mean DMFS score in 12-year olds showed a constant decline, from 13.7 in 1973 to 2.0 in 1988. The half in the decline of caries in the deciduous dentition of these 6-year-old cohorts is regarded as a warning that caries may be on the increase again in this part of The Netherlands. Regular monitoring is therefore required. Explanations for this halt in the decline of caries are discussed.