We evaluated the outcome of public oral health services in relation to the treatment mix in the city of Helsinki, in which 7 independent districts provided dental care to 98,000 patients in 1989. Outcome was defined as the increase in numbers of DMF teeth over the 2 years from 1989 to 1991 in 16,000 patients 8, 10, 12, and 13 years of age. The share of each type of treatment in the treatment mix was calculated on the basis of the market price of the items of service. The greater the share of prevention, the more positive the outcome (p<0.01)–that is, the lower the increase in numbers of DMF teeth. In a regression model the share of prevention alone accounted for 53% of the variation in the outcome by district. Addition of the share of checkups to the model increased its explanatory power markedly (R2= 0.74). A positive outcome was seen both in districts with poor and in those with good educational structures.□Children; dental health; effectiveness; evaluation; prevention