This study investigated the effects of an 8-wk aerobic training program on the serum levels of serotonin and in the changes in the symptoms of depression in elderly women. The sample of this study was divided in two groups: experimental (n=28) and control (n=20), with 58.6±6.4 and 56.8±5.1 years old respectively. The serum levels of serontonin were significantly reduced (p<0.05) in the experimental group when compared to the control group. A significant improve (p<0.05) in the symptoms of depression was also observed. This study demonstrated that 8-wk with 5 d.wk-1 of moderate and progressive aerobic training emphasizing walking can safely cause significant reduction in the serum levels of serontonin and improve the symptoms of depression in elderly women.