Extra-cellular levels (serum) of heat shock protein 70 is influenced by various stressors such as exercise and it has been shown that this protein affects the proinflammatory cytokines in human and animal samples. The aim of this study was to investigate the effect of endurance training on serum levels of proinflammatory cytokines (TNF-?, IL-1?, IL-6 and Hsp70) in trained and untrained rats. For this purpose, 10 male wistar rats were purchased from Pasteur institute of Iran and divided into control (n=5) and experimental (n=5) group. The aerobic program included 8 weeks (5 sessions per week) of endurance exercise running on a treadmill; exercise intensity was 55% to 75% VO2max. Serum levels of TNF-?, IL-1?, IL-6 and Hsp70 were measured by Elisa method. Results showed that serum levels of Hsp70 in the exercise group significantly increased (P<0.05). On the other hand, the level of IL-6, TNF-? and IL-1? did not significantly change between training and control group. Therefore, endurance training can protect cells and enhance immune system through increasing serum levels of Hsp70.