The effect of 3 different rest periods on the acute hormonal responses to resistance exercise (RE) was examined in 10 experienced resistance trained men (age: 20.37 +/- 2.24 years, weight: 65.5 +/- 26.70 kg). On 3 separate sessions of an RE protocol, subjects were assigned in a random order a rest interval of 60 seconds (P60), 90 seconds (P90), or 120 seconds (P120) between sets. The RE session consisted of 4 sets of squat and bench press to failure using 85% of 1 repetition maximum. Blood draws occurred at pre-exercise (T0), immediately post (T1), and 30 minutes post (T30) exercise for measurement of serum growth hormone (GH), testosterone (TS), and blood-lactate concentrations. Serum GH concentrations were significantly higher at T1 in P60 (64%) compared with P120. Also, serum TS concentrations were significantly higher at T1 in P120 (65%) and P90 (76%) compared to P60 (p < or = 0.05). Blood-lactate concentrations significantly increased at T1 for 3 protocols, but no significant protocols differences were observed. Although, training volume by using P90 and P120 was greater than that of P60, statistically a significant difference in training volume was not observed. The results of the present study support rest period in RE sets as an important variable to increase the anabolic hormone concentrations, and it should be mentioned that short rest intervals elevated greater increase in GH concentration compared with 120-second rest. However, TS response was greater in the RE protocol with a 120-second rest interval between sets.