Levels of circulating cortisol, testosterone, and testosterone-binding globulin were measured in 15 male wrestlers in relation to wrestling bouts and their outcomes. Concentrations of cortisol and testosterone increased consistently during wrestling bouts, while levels of testosterone-binding globulin dropped. Winners of competive matches showed greater increases in both cortisol and testosterone than losers. These findings indicate that humans, like other social mammals, may undergo specific endocrine changes in response to victory or defeat.