As aging advances, changes in mood and anxiety may imply greater risk of mood disorders, particularly anxiety and depression. Resistance exercise reduces anxiety and lessens risk of depression in the elderly, but little is known of the mechanisms involved. It was hypothesized that the human growth factor (IGF-1) may improve mood and anxiety in elderly participants given resistance training. 43 elderly men ages 65 to 75 years were randomly assigned to two groups, Control (n = 23) and high resistance Exercise (n = 20). After 24 wk., the Exercise group showed improved muscular strength and higher IGF-1 serum levels than the Con-trol group, as indicated by mean scores on a visual analogue mood scale and the State-Trait Anxiety Inventory. Intensive resistance training was efficacious in improving mood, anxiety, and IGF-1 serum concentration in elderly individuals free of clinical mood disorders.