The chronic autoimmune thyroiditis are heterogeneous entities by the functional, lesional and evolutive point of view. Ethiopathogenic factors involved in chronic autoimmune thyroiditis are genetical factors, combines with environmental factors, hormonal factors, infectious factors etc. The exact role of smoking on the autoimmune mechanism is unclear, but smoking is known to have an antithyroid effect.Our study tries to estimate the influence of smoking on serum levels of antithyroid peroxidase antibodies and antithyroglobulin antibodies, in a group of patients with various clinical forms of chronic autoimmune thyroiditis.We studied a group consists of 310 patients with chronic autoimmune thyroiditis, hospitalised in the Endocrinology Department of Constanta County Hospital, between January 2006 - December 2009. We detected serum values of antithyroidperoxidase antibodies and antithyroglobulin antibodies of our patients. We also followed the age, sex and presence of smoking in our study group. For statistical processing of the data we use Student's t-test.In our study group 24.28% of patients were smokers. Serum levels of antithyroid peroxidase antibodies were significantly increased (p < 0.001) in the smokers patients, compared with the nonsmokers patients. Serum levels of antithyroglobulin antibodies were significantly increased (p < 0.01) in smokers patients, compared with those who were nonsmokers.Smoking increased the serum levels of antithyroid antibodies in patients with chronic autoimmune thyroiditis.