Skin pigmentation differs between the sexes. In most populations, women exhibit lighter skin than men, which could be a consequence of requiring greater quantities of vitamin D to support pregnancy and lactation, of having more subcutaneous adipose tissue with less melanogenesis-stimulating androgens than men, and/or of a preference of males for fairer females(1,2). Among pre-pubertal children, however, girls are usually darker than boys, but this appears to reverse at the onset of puberty(1,3). We propose to use genetic variants strongly associated with age at menarche and Tanner stage (a measurement of pubertal development in adolescents)(4,5) to examine the relationship between puberty initiation and pigmentation changes, with particular emphasis on the consequences that these changes bring to sun exposure patterns and vitamin D levels, in ALSPAC children. Additionally, we will assess the role that androgens and estrogens play in eliciting gender pigmentation differences, using a similar framework.