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Both sexual selection and natural selection can influence the form of dimorphism in secondary sexual traits. Here, we used a comparative approach to examine the relative roles of sexual selection and natural selection in the evolution of sexually dimorphic coloration (dichromatism) and ornamentation in agamid lizards. Sexual dimorphism in head and body size were used as indirect indicators of sexual selection, and habitat type (openness) as an index of natural selection. We examined separately the dichromatism of body regions ’exposed to‚ and ’concealed from‚ visual predators, because these body regions are likely to be subject to different selection pressures. Dichromatism of ’exposed‚ body regions was significantly associated with habitat type: males were typically more conspicuously coloured than females in closed habitats. By contrast, dichromatism of ’concealed‚ body regions and ornament dimorphism …