This study focused on the effect of lead exposure on the thyroid gland. The study included 100 male workers employed in a lead smelter (mean duration of exposure 16.99 ± 5.63 years) and 60 healthy workers as a control group. Both groups underwent full clinical examination. Thyroid function tests comprising T3, FT3, T4, FT4 and TSH and determination of anti thyroid and antinuclear antibodies were performed. There was no statistically significant difference in measures of thyroid function between exposed and control groups. However, significant negative correlation was observed between FT4 and blood Pb level above 50 μg/dl. Anti thyroid antibodies were detected in the sera of 22 out of 38 of the exposed examined workers. The study also revealed existence of antinuclear antibodies in some of the exposed workers.