DMF teeth and surfaces were recorded in a random sample of 35-yr-old Oslo citizens (born 1949). The index values were related to selected independent variables: sex, years at school, oral hygiene status (OHI-S), periodontal conditions (PI), use of interdental cleaning devices and dental visiting habits. Data from the present investigation were analysed together with data from a similar study on 35-yr-olds in 1973 in order to detect possible changes over time. The mean DMFS-score in the present investigation was 85, indicating a high caries experience, mainly due to a high F-component. A statistically significant increase in the number of decayed surfaces was demonstrated concomitant with an increase in PI- and OHI-S scores. There were more carious surfaces among irregular dental visitors than among the regular visitors. No statistically significant differences in DMF-scores from 1973 to 1984 were detected, but there was a statistically significant reduction in the prevalence of untreated caries during this period. Furthermore, an increase in the number of filled surfaces from 1973 to 1984 and a reduction in the number of missing surfaces were registered. This may indicate a tendency towards restoring instead of extracting carious teeth during the last decade.