OBJECTIVE: To study risk factors for respiratory tract infections (RTIs) in children aged 2-5 years. DESIGN: A questionnaire was used to chart the number of visits to doctors and the number of antibiotics courses because of RTIs during a 1-year period. The risk factors studied were age, sex, birth weight, breastfeeding, atopy, siblings, smoking and childcare. SETTING: The catchment area of Oxie health centre in southern Sweden. SUBJECTS: 190 pre-school children. MAIN OUTCOME MEASURES: Number of visits to doctors and number of antibiotics courses. RESULTS: The risk of having to consult a doctor, as well as the risk of receiving treatment with antibiotics, because of RTIs was greater among children at daycare centres than among children who were mostly at home (adjusted OR 2.78 (95% CI 1.34-5.78) and 2.73 (1.38-5.43), respectively). CONCLUSION: Attending a daycare centre is the most important risk factor for RTIs in children aged 2-5 years.