en Radiation Biology Radiation Biology تحقيق بديع Original Research <span style="font-weight: bold"> Background:</span> Radon and its short-lived decay products are considered as the important sources of public exposure to natural radioactivity. The synergistic interaction between tobacco smoking and radon is known to be an actual problem. This study has provided a mathematical description and prognosis of the carcinogenic effects after combined action of radon with smoking. <span style="font-weight: bold">Materials and Methods: </span>A simple mathematical model was adjusted for the optimization and prognosis of the synergistic interaction of radon with smoking. The model postulates that the occurrence of synergism is to be expected as a result of additional carcinogenic damage arising from the interaction of sublesions induced by the two agents under consideration. <span style="font-weight: bold">Results:</span> The predictions of the model were verified by comparison with experimental data published by other researchers. The model appears to be appropriate and the predictions valid. <span style="font-weight: bold">Conclusion: </span>The suggested mathematical model predicts the greatest level of synergistic effect and condition under which this level is reached. The synergistic effect appeared to decline with any deviation from the optimal value of the ratio of carcinogenic effective damages produced by each agent alone. <br>Iran. J. Radiat. Res., 2007 4 (4): 169-174 Radon, smoking, synergistic interaction, mathematical model, carcinogenesis. 169 174 http://ijrr.com/browse.php?a_code=A-10-1-219&slc_lang=en&sid=1 J.K. Kim jkkim@kaeri.re.kr 79003194753284600665 79003194753284600665 Yes S.A. Belkina 79003194753284600666 79003194753284600666 No V.G. Petin 79003194753284600667 79003194753284600667 No