Abstract:This critical review discusses the use of the testosterone/cortisol ratio in the studies of athletic performance and sports physiology. Although in most of the time physical exercise is beneficial to health, it can also be seen as a "stressor" both in men and in women. It is not completely known at what level this "physical stress" ends up its beneficial effects and begins to impair health status. In search for this putative turning point, several markers have been put forward in the last decades. One of these markers is the ratio between testosterone, considered as an anabolic hormone, and cortisol, considered as a catabolic one. Whether in search for an anabolic internal environment for strength training or to avoid performance decline during aerobic workout, the testosterone/cortisol ratio has been considered as an important physiological variable to gauge individual conditioning and responses.