Introduction: The prevalence of autoimmune thyroid disease (AITD) had been shown to be markedly increased Diabetes Mellitus Type I (DM1). Some report have indicated that AITD is ten times more commonl in DM1 than in the general population, as might be expected due to the autoimmune nature of the two diseases. However it is difficult to find report regarding the incidence of AITD in type2 DM2, although this condition accounts for the majority of the population with hyperglycemia.Objective: This study aimed to determine the prevalence of AITD in diabetic patients.Materials and Methods: This cross sectional study was on 62 performed patients with DM2, and 601 DM2, for a total of 633. The subjects were selected randomly from diabetic out patients of an endocrine clinic. There were 467 women and 196 men with both types of diabetes with an age range of 8-84 years. One screening basis all patients had thyroid function testing (at least a sensitive TSH).Results: Overall 39 patients (5.8%) had AITD (Graves disease and Hashimototos thyroiditis). The incidence of AlTD was 8% and 5.6% in DM) and DM2 respectively. However the prevalence of AITD in DM1 was more striking. Because these patients were younger, and at age when generally AITD is more unusual, the incidence of AlTD in DM2 was surprisingly high, but may be accounted for by the older ages of these patients.Conclusion: There is definitely an increased prevalence of AITD in patients with DM2 as well as DM1. While in contrast with latter this may not represent a true disease association, the merit of screening for thyroid function in type 2 diabetes is questionable.