Small deviations from bilateral symmetry (a phenomenon called fluctuating asymmetry [FA]) are believed to arise due to an organism's inability to implement a developmental program when challenged by developmental stress. FA thus provides an index of an organism's exposure to adverse environmental effects and its ability to resist these effects. If one wishes to choose an individual with good health and fertility, FA could be used as an index of a potential partner's suitability. To explore whether this theory can be applied to human female bodies (excluding heads), we used a specially developed software package to create images with perfect symmetry. We then compared the relative attractiveness of the normal (asymmetric image) with the symmetric image. When male and female observers rated the images for attractiveness on a scale of 1 to 10, there was no significant difference in attractiveness between the symmetric and asymmetric images. However, in a two-alternative forced-choice experiment, the symmetric image was significantly more popular. The evidence suggests a role for symmetry in the perception of the attractiveness of the human female body.