Contemporary accounts of sex differences in perceptual-motor performance differ in their emphasis on nature and nurture. Study 1 examined the effect of extensive training on one of the largest sex differences, namely accuracy in dart throwing, and found that physical differences in height and reach could not explain sex differences in regional/national level dart players. Study 2 rejected accounts of sex differences based on participation rates by showing that male players recruited from a relatively small pool of club players were superior to the best female players selected from a much larger pool at the international level. Alternative accounts of the source of sex differences in darts, based on male and female players' differential development and practice histories, are discussed. (Contains 2 tables, 1 figure and 5 notes.)