• Three and 4-year-old children from two suburban preschools were individually interviewed to assess their knowledge of the effects of ingesting a household product, a candy, and a common drug. Most children understood that scouring cleanser was toxic. Children reported that candy was safe to eat, even in large amounts. However, vitamins were not perceived by all children as having a dose-related toxicity. This understanding developed with age, and boys were better than girls at differentiating between a usual and an excessive dose of vitamins. One overdose occurred, perhaps because of an increase in the child's interest in vitamins after the interview. More research is needed to broaden our understanding of children's knowledge of the toxicity of poisons. The results of the present study provided information needed for the formulation of educational objectives for a preschool poison prevention program. We believe the primary message is that nothing should be eaten unless it is approved by an adult.