Abstract: There is increasing evidence showing that both environmental androgens and environmental estrogens presented in our surroundings. But little is known about the status of environmental androgens in our living environment and the effects of environmental androgens in wildlife. The objective of this study is to evaluate the usefulness of guppies as an integrated bioassay which can be used to detect both environmental androgens and environmental estrogens at the same time. The size of orange spots in male guppy is proposed to be used as an endpoint to detect environmental androgens and the induction of vitellogenin is used as an endpoint to detect environmental estrogens. In addition, the potential mechanism of increase orange pigments induced by testosterone and/or environmental androgens will be examined by pteridine biosynthesis pathway.