AIMS: The purpose of this study is to investigate the changes of tumor markers with increasing utilization area in recent years in Hashimoto’s thyroiditis patients with subclinical hypothyroidism. METHODS: The serums of 30 newly diagnosed Hashimoto’s thyroiditis patients with subclinical hypothyroidism were collected before and 6 weeks after the treatment with L-T4. Thirty healthy volunteers were taken as the control group. TSH, thyroid hormones, anti-TPO, anti-T, CA 19-9 and CA 72-4 were studied in all patients. RESULTS: There was no significant differences in the levels of CA 19-9 and CA 72-4 in Hashimoto’s thyroiditis patients with subclinical hypothyroidism compared to the control group (p = 0.35 and p = 0.45, respectively). Significant difference was found in CA 19-9 value after the treatment with L-T4 (p = 0.04). Also a significant correlation between TSH and anti-TPO with CA 19-9 levels has been determined (p = 0.07, r = 0.484 and p = 0.001, r = 0.799, respectively). CONCLUSION: CA 72-4 studied for the first time in Hashimoto’s thyroiditis, has been determined as not different from healthy controls and the levels are not changed after the treatment with L-T4. To understand the reasons of why a significant increase has been shown in CA 19-9 after treatment, we believe that there is a need for long term new studies with more patients. Key Words: Subclinical Hypothyroidism, Hashimoto’s Thyroiditis, CA 19-9, CA 72-4