This study was performed to evaluate the relationship between biological markers of lead exposure and thyroid functions among male workers occupationally exposed to inorganic lead. 30 male workers exposed to inorganic lead at smelting and battery factories were investigated, and 30 male control workers who were not exposed to inorganic lead occupationally were chosen for this study. The data were obtained using direct interview and assessment of biological markers of lead exposure and thyroid indices. As biological markers for lead exposure, blood ZPP. blood lead, urine lead and hemoglobin were measured. As thyroid indices. TSH and FT4were determined. The results of the study were summarized as follows 1. Levels of ZPP, blood lead, and urine lead were significantly higher in lead-exposed group than in nonexposed control group(p<0.01 all). Hemoglobin level was significantly lower in lead-exposed group than in nonexposed group(p<0.01). 2. Study subjects had normal values of TSH and FT4 But TSH level was insignificantly lower in lead-exposed group than in nonexposed control group(p=0.11) and FT4 level was significantly lower in lead-exposed group than in nonexposed group(p<0.01). 3. As the result of simple regression analysis in lead-exposed group. FT4 level was negatively correlated with the amount of smoke, blood ZPP, and blood lead(p < 0.05 all). 4. In lead-exposed group, FT4 was used as a independent variable and age, the amount of smoke, blood ZPP, and blood lead were entered as a dependent variables in the model. As the result of multiple regression analysis with stepwise selection method, the amount of smoke and blood ZPP were negative predictors of FT4(p=0. 04, p=0.09, respectively). In conclusion, levels of TSH and FT4were lower in lead-exposed group than in nonexposed control group. In lead-exposed group, FT4 level was negatively correlated with amount of smoke, blood ZPP, and blood lead in simple regression analysis. To clarify this relation, further research between lead exposure and thyroid function may be required for worker with long-term lead exposure or high lead exposure.