The number of melanocytic nevi is the most important risk factor for cutaneous melanoma. This 1998 cross-sectional study of 1,812 children aged 2-7 years from 78 day-care centers in Germany analyzed the protective effect of sunscreen and clothing on the number of melanocytic nevi. Total body nevi were counted, and pigmentary features were assessed. Parents underwent a standardized interview concerning their children's sun exposure and sun-protective behavior. Almost 95% of the children had used sunscreen previously. Children who used sunscreen and wore more clothing spent significantly longer periods on holidays in sunny climates (p < 0.001 and p = 0.006, respectively) and had a higher outdoor activity score at home (p < 0.001 and p = 0.012, respectively). Multivariate analysis adjusted for confounders showed no significant protective effects of applying sunscreen. Examination of the potential protective effect of clothing revealed an inverse dose-response correlation between the number of clothes worn at the beach or outdoor swimming pool and the number of melanocytic nevi (p < 0.001, adjusted for confounding). Randomized controlled trials are needed to confirm these results. Meanwhile, public education should aim to protect children primarily by sun avoidance and protective clothing, while sunscreen should also be used.