We observed the response of serum growth hormone (GH) and testosterone (T) to a progressive resistance strength training program. Basal levels (after a 12-h fast) of GH and T were measured in young (23 years) and elderly (63 years) subjects before and after a 12-week training program. The response of GH and T to an acute bout of exercise was also measured. The exercise training, which involved all the major muscle groups, was conducted on Nautilus equipment and required 45-60 min for completion. The subjects completed three sets of lifts with 8-10 Reps/set. Blood was drawn from an anticubital vein, centrifuged (1169 g) for 15 min and the serum frozen for later analysis. The acute exercise blood samples were taken immediately before and after the exercise and at 15 min post-exercise during week 1 and 12. The hormone assay was carried out with radioimmunoassay kits for GH and T. The basal level of GH increased by % in the young and by only 3% in the elderly but neither change was significant. In response to a single exercise session GH levels in the young went from +/- to +/- ng/ml before training and from +/- to +/- after training. Each response was significant (P less than ) as were the pre-post differences (P less than ). In the elderly the response was not as great, values increasing from +/- to +/- ng/ml before training and from +/- to +/- ng/ml after training were recorded. These differences represented significant increases (P less than ) but did not demonstrate pre- to post-changes. Basal levels of T decreased in both groups, but were not significant. The T response to an acute bout of exercise was not significant but did increase in both age groups. In conclusion, the data presented here indicate that strength training can induce growth hormone and testosterone release, regardless of age, but that the elderly response does not equal that of the young.