This study compared trained and untrained subjects' responses to a single bout of weight-training exercise of the same relative intensity. Young men (N = 21) were divided into three similar groups based on their 1-RM dead-stop squat. Group 1 (n = 8) was made up of well-trained weightlifters (TWL). Group 2 (n = 7) were untrained subjects who took part in the exercise session (UTWL). Group 3 (n = 6) served as untrained controls (C). Food and drink were controlled and measured. Heart rate, profile-of-moods states, and blood samples were taken three times before and five times after exercise. Blood was analyzed for hematocrit (Hct), lactate (HLa), blood glucose (glu), free fatty acids (FFA), insulin (I), glucagon (G), cortisol (Cort), growth hormone (hGH), epinephrine (E), and norepinephrine (NE) using standard methods. Data were analyzed using ANOVA with a repeated-measures design. The alpha level was p≤0.05. The single exercise session elicited significantly higher HR, HLa, glu, FFA, hGH, E, and NE values in the TWL and UTWL 5 min postexercise than in the C group. UTWL Cort values were significantly higher than the TWL or C groups at 5 min postexercise. At 1-1/2 hrs postexercise the UTWL had significantly higher values for HR, HLa, and Cort than the other groups. The UTWL had significantly higher FFA concentrations compared to the Controls at 20 hrs postexercise. Shifts in plasma volume did not adequately account for the observed changes in HLa, glu, or hormones. These data suggest that the magnitude of the response to weight-training exercise is related to the subject's trained state. Additionally, these data indicate that weight training can stimulate increased FFA concentrations at various times during recovery.