Abstract The Wilson Sex Fantasy Questionnaire was given in Japanese translation to 60 male and 71 female student teachers aged 18–20. Principal-components analysis with Promax rotation, conducted separately for men and women, revealed a structure similar, though not identical, to that found with British subjects. Japanese subjects reported a much lower frequency of sex fantasy all round than British subjects, but the pattern of male-female differences was identical between the two cultures. Males report more active fantasies than passive, whereas female fantasies are predominantly passive. Similarly, males report more impersonal fantasies than sadomasochistic, but with females the reverse is true. This cross-cultural consistency lends support to a biological interpretation of gender differences in sexuality.