Exercise is a potent physiological stimulus for the release of growth hormone (GH), cortisol, testosterone and prolactin, and also inhibits insulin release. These hormones may have roles in substrate metabolism during and after exercise, but different types of exercise may produce varying hormone responses. The aim of this study was to investigate the hormone response to different types of exercise in young men. Eight men aged 18-25 years were familiarised before completing three trials, at least 7 days apart, in a random order: 30-s cycle-ergometer sprint (Sprint); 30-min resistance exercise bout (Resistance); 30-min cycle at 70% VO2max (Endurance). All trials took place in the morning following an overnight fast. Blood samples were taken pre- and immediately post-exercise, and 20, 40 and 60 min post-exercise. Area under the curve (AUC) was calculated using the trapezoid method. Differences between means were investigated using ANOVA and Bonferroni adjusted t-tests. Statistical significance was accepted at P < 0.05. In the endurance trial there was a significant increase from pre-exercise to peak concentrations for GH, cortisol, prolactin and testosterone, and a significant decrease in insulin with no change in glucose concentrations. In the sprint trial there was a significant increase in GH, cortisol, testosterone and glucose concentrations and in the resistance trial there was a significant increase in testosterone and glucose concentrations. Endurance exercise elicited the greatest AUC for GH and testosterone and the greatest suppression of insulin concentrations. Sprint exercise caused the greatest AUC for cortisol, prolactin and glucose concentrations (Table 1). The nature and magnitude of the hormone response was influenced by exercise type, perhaps reflecting the roles of these hormones in regulating substrate metabolism in the face of differing demands during and after resistance, sprint and endurance exercise.