OBJECTIVE: The aim of this study was to investigate caries and its determinants in preschool children with and without asthma, followed from 3 to 6 years. METHODS AND SUBJECTS: Caries, plaque, and gingivitis were examined at 3 and 6 years of age in 64 asthmatic children and 50 matched, healthy control children. Furthermore, at 6 years radiographic examination and saliva sampling were conducted. The parents were interviewed about various oral health-related factors. RESULTS: Initial caries increment between 3 and 6 years of age was statistically significant higher for children with asthma compared with children without asthma (P < 0.05). Asthmatic children had more bleeding gingivitis and a higher consumption of sugary drinks than healthy children at 3 years of age (P < 0.05). At both 3 and 6 years of age, the asthmatic children were more frequently mouth breathers than healthy children, only statistically significant for 6-year olds (P < 0.05). CONCLUSION: Preschool children with asthma at 3 years of age run a higher risk of developing caries lesions until 6 years of age compared with children without asthma. Children with asthma have a higher prevalence of bleeding gingivitis, a higher intake of sugary drinks and are more frequently mouth breathers than preschool children without asthma.