Aim of the work: this study aimed at exploring the effects of lead and cadmium on the thyroid function of workers of welding operation are exposed to welding fumes containing various toxic metals. Subjects and Methods: the level of blood lead and cadmium was measured by atomic absorption spectro-photometry. Thyroid stimulating hormone, free thyroxin, free triiodothyronine in serum were estimated by enzyme immunoassay. Results: the workers with higher level of blood lead level (BLL) (30-60) ug/dl showed high thyroidstimulating hormone level (0.50-9)uIU/ml andno changes in free thyroxine and free triiodothyronine. No changes in free thyroxine, free triiodothyronine and Thyroid-stimulating hormone level in relation to increase in cadmium level. Conclusion: we concluded that higher level of blood lead may cause certain damage to thyroid function leading to subclinical hypothyroidism. We concluded no relation between cadmium level and thyroid hormones. The smokers have higher cadmium level (0.59-9.6)ug/L.