Acute suppurative thyroiditis (AST) is a rare disorder. The rarity of AST is a result of the resistance of the thyroid gland to local infection. Thyroid function tests are usually normal in AST. In a review of the literature from 1966 to 1995, only three cases of AST associated with thyrotoxicosis have been convincingly demonstrated. The thyrotoxicosis in these cases was caused by diffuse inflammation of the thyroid gland and to the disruption of follicles with the release of pre-formed thyroid hormone into the circulation. Thus, the thyrotoxicosis in these cases was transient. With successful therapy, nearly all patients showed complete recovery of thyroid function within two to three months. The patient in the case here was a diabetic woman with Graves' disease in whom thyrotoxicosis occurred after Klebsiella pneumoniae thyroiditis, with relapse nine months after discharge. Thus, the patient's thyrotoxicosis might not have been caused simply from thyroid tissue destruction by AST, but also as a result of enhancing autoimmune activity. No previous case has ever been reported in the English literature. In diabetics, the impairment of chemotaxis and phagocytosis has been noted. Therefore, diabetes mellitus (DM) might have been the precipitating factor for this patient's acquiring this unusual infection. Thyrotoxicosis and AST will increase insulin requirements and thus aggravate diabetes. In addition, poor control of blood sugar will enhance the severity of AST.