The aim of this study was to investigate changes in immunoreactivity of Ras and Raf-1 in lung epithelial cells of rats exposed to carcinogen NNK after swimming training. 50 Wistar rats were randomly divided into five groups: control, training, training + NNK, NNK and sham. NNK-induced groups received NNK Subcutaneously once a week at a dose of 12/5 mg per kg body weight for 12 weeks. The exercise training consisted of submaximal swimming training for 12 weeks. The percentage of reaction of Ras and Raf-1 in lung epithelial cells were measured by HIC. It was observed no significant change in the Ras and Raf-1 immunoreactivity of lung epithelial cells in training group compared to control. A significant incretion of the Ras and Raf-1 immunoreactivity was found in NNK group compared to control group (p=0.001). Furthermore, a significant reduction of the Ras and Raf-1 immunoreactivity was observed in exercise + NNK group when compared to NNK group (p=0.001). Generally it could be confirmed that regular submaximal aerobic training plays an important role in inhibition of the effects of lung carcinoma induced by NNK via reduction of Ras and Raf-1 activity.