Abstract: Asbtract20 cases with subacute thyroiditis were examined with SPECT. The results showed that 12 with bilateral thyroid enlargement proved the underdevelopment or nondevelopment of bilateral thyroid, 8 with unilateral thyroid enlargement and 4 with bi1ateral thyroid the underdevelopment, 4 unilat eral or localized underdevelopment. These show that SPECT has a definite reference value in the diagnosis of subacute thyroiditis and other thyroid diseases and thyroid carcinoma in particular.