The use of medical care among 880 1-5 year olds in different day care settings was studied using register information on physician visits, purchases of antibiotics and municipal day care in 1984. The unit of analysis was months in the different day care settings and not children. The rates of physician visits were 1.4 to 1.8 times higher for acute upper respiratory tract infections and all acute infections and 2 to 3 times higher for secretory otitis media during day care centre months and family day care months as compared to home care months. The rate of visits for bronchial asthma was 5 times higher during day care centre months than during home care months. No differences were found between day care centre months and family day care months with respect to the rates of physician visits for acute upper respiratory tract infections, acute otitis media and all acute infections. Among children in family day care, the daily number of hours in day care, and size, average age and age homogeneity of the groups were not significantly associated with rates of visits for all acute infections or purchases of antibiotics.