To examine changing patterns regarding restorative treatment criteria for dental caries. A representative sample (n = 215) was drawn from all 15-year-olds receiving dental treatment in the Public Dental Service (PDS) in Oslo, Norway for each of the years 1979, 1989, 1993 and 1996. Information from clinical records and bitewing radiographs on caries treatment was collected. The results presented in this paper pertain to 198, 201, 209 and 208 subjects in each group. The results revealed dramatic changes in the use of restorative treatment criteria. Only 16% of tooth surfaces were treated in 1996 according to the criteria from 1979. The number of sound surfaces was found to have increased by 39% whereas the number of filled surfaces was reduced by 92%. In spite of more stringent criteria for restorative treatment, the number of D4 lesions did not increase. The practice of change in restorative treatment continued during the 17 years of study. Though the number of decayed surfaces appeared to be stable during the period, in reality, there was a reduction in caries occurrence during the first 10-year period (1979-1989). A conceptual model of dentists' caries-related treatment decisions outlined by Bader & Shugars may be used to explain parts of the rapid change in the criteria used in the PDS in Oslo.