The present work focused on the detection of immunoglobulins IgG, IgA, IgM and C3 complement in a wide variety of thyroid diseases as well as in normal thyroid tissue to evaluate the immunologic nature of these lesions. The study was encountered on 111 thyroid specimens selected from the biopsies received at the Pathology Laboratory over a period of 5 years. Formalin fixed paraffin embedded sections were prepared and stained by H and E and immunoperoxidase technique. IgG, IgA and IgM were detected in varying degrees in all types of thyroid lesions and also in normal thyroid tissue. While, positivity for C3 complement was detected in [6/10] cases of toxic nodular goiter, all cases of cretinism with goiter 8, in 11 out of 13 cases of Graves disease, in 14 out of 19 cases of thyroiditis and in 10 out of 16 cases of papillary carcinoma of the thyroid gland. However, no C3 complement could be detected in normal thyroid tissue, in cases of simple goiter, in all cases of thyroid adenoma and in all cases of follicular, anaplastic and medullary carcinoma examined. Results indicated that immunoglobulins are not predictors for diagnosis of autoimmunity in thyroid diseases, but are best considered as indicators for the gland activity. However, C3 and immunoglobulins may be used as useful markers for the diagnosis of papillary carcinoma and its follicular variant from follicular carcinoma