NEW YORK, June 14 (Praxis Press) Melanocytic nevi originate in childhood and are mainly caused by exposure to the sun. High nevus density is a risk factor for cutaneous malignant melanoma. Investigators examined 309 white schoolchildren over a period of three years. The children's parents received directions to apply SPF 30 broad-spectrum sunscreen to exposed sites when the child was expected to be in the sun for 30 minutes or more. Children in the sunscreen group developed fewer nevi than controls. A significant interaction was detected between the freckling and study group, indicating that sunscreen use was much more important for children with freckles than for children without (see paper). Sunscreen may be highly effective in protecting children against nevi and could therefore decrease the risk of melanoma later on in life.