Eighty-nine cases of hyperthyroidism and 20 cases of hypothyroidism caused by Hashimoto's thyroiditis were observed in order to analyse the thyroid and immune functions of the patients, and their relationship with the syndromes of TCM. The results showed that, in the patients with Yin deficiency syndrome, the contents of total T4, T3 were higher than normal and TSH lower than normal, while in Yang deficient patients, the contents of total T4, T3 were lower than normal and TSH higher than normal. This results suggested that the states of thyroid functions were closely related to the TCM syndromes. It was also found that the percentage of OKT 4+ cells and the self-recognizing ability of lymphocytes were lower than normal in patients with hyperthyroidism and Yin deficiency. While in patients with hypothyroidism and Yang deficiency, they were higher than normal. These meant that the abilities of lymphocyte autoreaction in Yin deficient patients were in contrary tendency with those in Yang deficient patients. The former had the manifestation of over-inhibition while the latter, hyperaction. Besides, the contents of auto-antibodies were higher than normal in both the patients with hyperthyroidism and hypothyroidism, which manifested itself as a common character of autoimmune thyroid diseases. The results indicated that there were common characters as well as individual characters of thyroid and immune functions between hyperthyroid patients and hypothyroid patients, and these characters might well be the material bases of various syndromes in TCM.