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 thyroid-stimulating 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.