We reported 3 patients with pernicious anemia associated with chronic thyroiditis and evaluated their immunological abnormalities in this paper. Two patients were females and another was male. They were all advanced in age. Levels of gammaglobulin including IgG was elevated in patients' sera. Values of complement components were within normal ranges. Although organ specific autoantibodies against intrinsic factors, parietal cells and thyroidal tissue antigens were detected, organ non-specific autoantibodies such as anti-DNA and/or anti-ENA antibodies were negative in the patients' sera. Percentage of T cells in peripheral blood remained within normal ranges. However, ratio of helper T/suppressor T cells was reduced considering patients' age. Moreover, Mantoux tests were negative in all of three patients. These results suggested that impaired cellular immunity, particularly imbalance of T cell subsets, caused by senescence, simultaneously induced pernicious anemia and chronic thyroiditis in these patients.