We hypothesized that the substantial difference in incidence of eating disorders between men and women would be correlated with a similar difference in sociocul-tural norms promoting thinness. The 10 popular magazines most commonly read by young men and young women were examined for advertisements and articles promoting weight loss or shape change. The women's magazines contained 10.5 times as many advertisements and articles promoting weight loss as the men's magazines (p <.005), the same ratio reported from several sources for cases of anorexia nervosa. Men, however, were disproportionately subjected to incentives to change body shape compared to weight loss (p <.01). This study supports the hypothesis that the comparative frequency of eating disorders in males vs. females is more closely related to the differing extent of gender-related reinforcement of related dieting behavior than any known biological parameter. It is plausible that a dose-response relationship exists between sociocultural reinforcements promoting thinness and the incidence of eating disorders in any particular population group.