Two purported cues to female physical attractiveness are body mass index (BMI) and body shape as measured by the waist-to-hip ratio (WHR). This study examined the relative contribution of both cues in two culturally distinct populations. Eighty-two male participants from Britain and Japan were asked to rate a set of images of real women with known BMI and WHR. Results showed that BMI is the primary determinant of female physical attractiveness, whereas WHR failed to emerge as a significant predictor. Results also showed that there were significant differences in preferences for physical attractiveness, with Japanese participants preferring images of women with significantly lower BMIs than Britons. Finally, results showed that the Japanese are more reliant on body shape than Britons when judging physical attractiveness. The findings are discussed in terms of evolutionary psychological explanations of mate selection, and sociocultural theories which emphasise the learning of preferences in social and cultural contexts.