OBJECTIVE To study a quantitative method of health risk assessment for occupational exposure to benzene, and to provide theoretical basis for occupational health risk research in our country. METHODS The probability of the occurrence of cancer during the lifetime of individual exposed to an agent at dose D during lifetime was estimated by using dose-response models. The relationships between internal dose of substance in question and the probability of occurrence of a tumor could be formulated by probit model, logit model, Weibull model, one hit model, multi-hit model, or multistage model. The functions between internal dose and exposure concentrations could be obtained by pharmacokinetic analysis or human epidemiological data fitting. Then, by incorporating these functions into dose-response models, the risk at various exposure levels of exposed populations could be estimated. RESULTS The risk of workers exposed to benzene in a plant was estimated by two-stage model, one hit model and Weibull model respectively, given the concentrations of benzene. The dose-response curves obtained from three models were all linear. The risk at mean concentration 7.25 mg/m3 were 7.50 x 10(-4), 1.83 x 10(-4), 2.31 x 10(-6) respectively. The value by two-stage model was maximal and the value by Weibull model was minimum. CONCLUSIONS This method can be used to assess the risk of exposure to hazardous substances in the workplace, and lifetime cancer risk of exposed populations can be estimated.