The aim of this study was to investigate the effectiveness of a school-based fortnightly 0.2% sodium fluoride mouthrinse programme after children ceased to participate. The programme, which commenced at age 6 and ceased at age 12, was investigated 4 years following its cessation. Three groups of 12-year-olds and three groups of 16-year-olds were examined, i.e. children who had participated in the mouthrinse, those attending non-participating nearby schools and lifetime residents of a fluoridated community. Significant differences in mean DMFT in the 12-year-olds between the mouthrinse and the control group were not found in the 16-year-old group. Mean DMFT for the mouthrinse group and those in a fluoridated community (which were the same in 12-year-olds) showed a statistically significant difference in those aged 16. Most caries found, both in 12-year-olds and in 16-year-olds, occurred on molar teeth and was found on pit and fissure surfaces. The cessation of these programmes at age 12 should be reappraised and the combination of school-based fluoride mouthrinse programmes with a fissure sealing programme is recomended.