The fading of nine reactive dyes on cotton fabrics under light and perspiration was investigated using the ATTS standard and many factors affecting the stability of these dyes were discussed, viz. exposure environment, chromophores of dyes, the pH value and components of the artificial perspiration. The experimental results show that reactive dyes exhibit lowest stability under simultaneous exposure to light, perspiration and oxygen in a wet state. Among all selected dyes, Cu-complex azo reactive dyes appear to be the most sensitive, whereas anthraquinone reactive dyes show the best stability. The pH value of perspiration may also greatly influence the fading of dyes by affecting the hydrolytic stability of dye-fibre bonding. Furthermore, the study on the contribution of artificial perspiration components discloses that some acidic components play major roles in the fading of the dyes and inorganic salts usually decelerate the fading extent.