We assessed the effects of aerobic and/or resistance training on thermoregulatory responses in older men and analyzed the results in relation to the changes in peak aerobic capacity (Vo_{2, peak}) and blood volume (BV). Twenty-three older men (age, 64 ± 1 yr; Vo_{2, peak}, 32.7 ± 1.1 ml^.kg^-1.min^-1, mean ± SE) were divided into 3 training regimens for 18 weeks; control (C, n = 7), aerobic training (AT, n = 8), and resistance training (RT, n = 8). Subjects in C were allowed to perform walking of ~10,000 steps per day, 6~7 days per week. Subjects in AT exercised on a cycle ergometer at 50-80% Vo_{2, peak} for 60 min per day, 3 days per week, in addition to the walking. Subjects in RT performed a resistance exercise including knee extension and flexion at 60-80% of 1RM, 2-3 sets of 8 repetitions per day, 3 days per week, in addition to the walking. After 18-wk training, Vo_{2, peak} increased by 5.2 ± 3.4% in C (P > 0.07), 20.0 ± 2.5% in AT (P < 0.0001), and 9.7 ± 5.1% in RT (P < 0.003), but BV remained unchanged in all trials. In addition, the esophageal temperature (T_es) thresholds for forearm skin vasodilation and sweating, determined during 30-min exercise of 60% Vo_{2, peak} at 30°C, decreased in AT (P < 0.02) and RT (P < 0.02) but not in C (P > 0.2). In contrast, the slopes of forearm skin vascular conductance/ T_es and sweat rate/ T_es, remained unchanged in all trials, but both increased in subjects with increased BV irrespective of trials with significant correlations between the changes in the slopes and BV (P < 0.005 and P < 0.0005, respectively). Thus, aerobic and/or resistance training in older men increased Vo_{2, peak} and lowered T_es thresholds for forearm skin vasodilation and sweating, but did not increase BV. Further, the sensitivity of the increase in skin vasodilation and sweating at a given increase in T_es was more associated with BV than Vo_{2, peak}.