Sun protection in childhood is important to reduce the risk of developing skin cancer later in life. The "Periods-of-Life-Program" for primary prevention of skin cancer introduces a combination of individual and environmental interventions for the preschool period. Within this pilot study, an intervention group received cognitive-behavioral and environmental interventions. A control group had solely received the environmental intervention, and a wait-control group received no intervention. Nursery school children (n=80, 3 to 6 years of age) of four nursery schools were randomly assigned to these groups on school level. The ability of the cognitive-behavioral intervention (a theater play) to enhance sun protection knowledge was examined. The theater play improved knowledge over all age groups (p.05 [eta]2=.06). Age-specific analyses showed better results for children aged 5 to 6 (p.05 [eta]2=.20) compared to children aged 3 to 4 years (p=.17 [eta]2=.04). In combining cognitive-behavioral and environmental interventions, the "Periods-of-Life-Program" is a promising strategy for primary prevention of skin cancer. (author abstract)