Patients with the general type (patient #1 and #2) and the selective pituitary type (#3) of thyroid hormone refractoriness (TR) were studied to clarify defects at peripheral and pituitary receptors. Products of T3 and TSH (n = 63) were calculated when T3 was above the normal limit (T3 > 1.8 ng/ml, 2.8 nmol/l) as one of the indices of pituitary resistance. Means of T3 (ng/ml) x TSH (mU/l) of patient #1 (mean; 40.8), #2 (15.0) and #3 (8.6) were significantly greater than patients with Graves' disease (2.1), suggesting pituitary refractoriness in the 3 patients. The products of patient #1 and #2 were also significantly larger than patient #3, demonstrating that the pituitary insensitivity in the latter (#3) was less than the former patients. Means of serum cholesterol in patients #1 and #2 were higher than patient #3 and patients with Graves' disease. Products of T3 (ng/ml) and cholesterol (mg/ml) (n = 28) in the patient #1 (541.9) and #2 (461.0) were significantly greater than the patient #3 (292.8) and the patients with Graves' disease (275.3). The results demonstrate generalized refractoriness in the patient #1 and #2 and selective pituitary resistance in the patient #3. It is suggested that our patient with the pituitary type (#3) had less severely affected receptors at the pituitary than our two patients with the general type. These results are consistent with the previous hypothesis that the pituitary type of TR is a partial form of this disease.