Aging is associated with quantitative loss of muscle mass (sarcopenia) and subsequentdecrement in muscle strength and functional abilities. Exercise can change the impact of someanabolic hormones including testosterone. This study was undertaken to determine the effect ofresistance and endurance training on blood testosterone concentration in old men(age 63.7±3.4yr ; n=45). Participants were assigned to three equivalent groups of control; endurance andresistance randomly (n=15). Endurance and resistance group underwent 8 weeks of training;three times per week. Endurance training consisted of 16min running at 50-55% MHR in week1reaching 60-70% MHR for 30min till 8th week. Resistance training was two sets with 10repetitions at 50% 1RM. The intensity of training was increased till week8 (3 sets; 6 reps at 60-70% 1RM). Blood samples were obtained before and after 4 and 8 weeks of training at rest.ANOVA test showed that testosterone concentration in both endurance and resistance group hadsignificant increase after 4 and 8 weeks of training (p<0.05). The hormonal changes producedby resistance and endurance training may be an important stimulus in older men contributing toprevention of sarcopenia.