Objectives: The aims of this study were to develop approaches for monitoring and prioritizing factors associated with thermal stresses imposed on workers in iron and steel casting industries, and to eventually purpose effective control strategies. Methods: The whole study was completed in the furnace areas of two steel casting and two iron casting plants, where the air temperature (T_a), radiant temperature (T_r), air velocity (V_a) and partial water vapor pressure (P_a) were measured continuously during two consecutive work cycles. Simultaneously, the metabolic rates (M) of all workers in the furnace area were also measured. Results: Using the WBGT as an index for screening purposes, our results suggest that all furnace area workers in both types of casting plants might experience severe heat stress. The predicted heat strain (PHS) model proposed by ISO 7933 was further adopted for detailed analysis from the physiological aspect. Through use of the Monte Carlo simulation and sensitivity analysis, both M and T_r were found to be the two most important factors associated with workers' thermal hazard. Therefore, two effective control strategies were suggested, including reducing workloads of workers and reducing radiant heat transmitting from furnaces to workplace environments. Conclusions: The approach developed in the present study would be beneficial to many other industries for initiating strategies to avert the thermal hazard imposed on workers.(J Occup Health 2014; 56: 505–510)