A large number of melanocytic nevi is the strongest known risk factor for melanoma in whites, but its relationship to sun exposure overseas among young white women living in temperate climates is unclear. A total of 754 white English women aged 18-46 years were recruited into a cross-sectional study in 1997-2000 to investigate the effect of ultraviolet exposures on numbers of nevi and atypical nevi, and on skin aging as measured by microtopography. Having ever holidayed in hotter countries was associated with a greater age- and phenotype-adjusted mean number of whole-body nevi (percent increase=74; 95% confidence interval: 24, 144; P=0.001), particularly for holidays taken at ages 18-29 years and for counts of the trunk and lower limbs. Having ever lived overseas was not associated with nevus counts, but was inversely associated with number of atypical nevi (P=0.02). Skin aging was not associated with residence or holidays abroad. The association of holidays overseas with an increased nevus count in young white women, which was stronger in the anatomical sites intermittently exposed to sunlight, supports the hypothesis that intermittent sun exposure is of relevance in the etiology of nevi and, hence, melanoma. The findings are of public health relevance given the growing popularity of foreign holidays.