A population survey was conducted to determine the incidence of injuries among preschoolers and their risk factors. A systematic sample (15%, n = 4540) of families with at least one child aged 0-5 years in 1991 living in the Canton of Vaud (Switzerland) received a mailed questionnaire in February 1992. There were 5827 eligible children in the sample. The response rate was 67.5% after two recall mailings. Injuries were defined as those from all causes with at least one physician contact in 1991. The overall incidence was 224 injuries per 1000 children (95% CI [= confidence intervall]: 211-237); 188 per 1000 children were injured over 1 year (95% CI: 176-200, n = 746), of whom 16.5% (n = 123) had 32 injuries. Falls represented 66% of all injuries, followed by burns (8%) and poisonings (5%). The proportion of hospitalized cases was 4.8% and the population incidence of hospitalization due to injury was 10.8/1000 children. Socioeconomic factors did not influence the occurrence of injuries. CONCLUSION: The measured incidence of injuries among preschoolers is among the highest in developed countries. Practitioners could contribute more effectively to injury prevention through routine information and counselling of parents from all social backgrounds.