In Sweden about 28 per cent of 3-year-old children have developed carious lesions. It has been shown that children below the age of 3 have the highest hospital emergency department visiting rate and receive prescriptions for medicines more often than older preschool children. Furthermore, studies have shown that immigrants more often use hospital emergency departments than Swedes. The purpose of this study was to describe illness and use of medicines in infants and toddlers with special reference to caries prevalence at 2 and 3 years of age and to immigrant status. The study was designed as a prospective study, starting with 671 children aged 1 year. The parents were interviewed about the child's medical history. The results indicate that illness during the first year of life can influence caries prevalence in 2 and 3-year-olds. However, this study could not show any difference in caries prevalence between children who had used medicines at an early age and those who had not. Furthermore, during the first year of life the immigrants had visited a physician more often, been admitted to hospital more and consumed more medicines that non-immigrants.