Background.  New perspectives are needed for oral health programmes (OHPs). The aim was to evaluate the preventive effect of a risk‐based OHP in comparison with a traditional programme.Design.  An age cohort of 794 Finnish children, 446 in the intervention group and 348 in the control group, was followed from 18 months to 5 years of age. The children were screened for mutans streptococci (MS) in the dental biofilm. The main outcome measure was the proportion of children with dental caries (decayed, missing, or filled primary teeth > 0) at the age of 5 years. The intervention, targeted to MS‐positive subjects in the intervention group only, was based on repeated health education to the caretakers and xylitol lozenges for the child. Dental hygienists carried out the programme.Results.  OHP was effective in white‐collar families [numbers needed to treat (NNT) = 3, 95% CI 2–11]. Factors significantly associated with caries at 5 years were MS colonization at 18 months, occupation of caretaker, but also gender when incipient carious lesions were included in the index.Conclusion.  Early risk‐based OHP, targeted to the families of MS‐positive children, can reduce the risk for caries in white‐collar families. For blue‐collar families, different kinds of methods in caries prevention and support are needed.