Magister Chirurgiae Dentium (MChD) / The study was carried out to 1) determine the effectiveness of the caries inhibiting effect of a weekly mouthrinsing programme in South African schools over a three year period and 2) compare neutral solutions of 0,2 per cent and 0,05 per cent NaF using a placebo of tapwater as control. Twelve to 13 year old White school children from eight randomly selected schools in the Parow School Board area of the Cape Peninsula were chosen. Participants were randomly assigned to one of the three rinsing groups. After three year's participation, the mean net increment in DFS per child was 4,7 for the 0,2 per cent NaF group; 5,9 for the 0,05 per cent NaF group and 7,5 for the placebo. These differences are statistically significant (p<:O,OOI). This meant a caries reduction of 38 per cent for the stronger and 21 per cent for the weaker sodium fluoride mouth rinse. It is concluded that such a mouth rinsing programme is a practical, feasible and an efficient approach to caries prevention in South African circumstances.