Objective: This study was conducted to quantify chronic lead exposure from various media(ie. working environment, food, ambient air), and to certify the usefulness of exposure assessment using Monte-Carlo simulation in the fields of occupational health. Methods: Data were obtained from Korean Industrial Health Association, Korea Food and Drug Administration, and the Ministry of Environment. Then lead worker`s exposure was estimated indirectly from various media and parameters (ie. volume inhaled, body weight, dietary intake, etc.). Uncertainty was analyzed by Monte Carlo simulation with Crystal Ball software. Exposure doses and hazard indices were simulated with various hypothetical scenarios including weekly working hours and respiratory protective equipment. Results: Without respiratory protective equipment, the total exposure dose per kilogram of body weight of lead workers was estimated as 5.45×10(-3) mg/kg/day, and hazard index was estimated as 2.26, and exposure contributions were calculated as follows: working environment(82.42%); foods(17.57%); and ambient air(0.01%). But, if working condition has changed-reduction of working hours and using respiratory protective equipment, the total exposure dose per kilogram of body weight was estimated between 1.34×10(-3)-1.49×10(-3) mg/kg/day, and hazard index was estimated between 0.56-0.62. Conclusions: This study suggested that occurrence of hazardous impact(ie. increased blood pressure) through lifetime lead exposure would be expected, and that the Monte-Carlo simulation was useful for the fields of occupational health.