201Tl/99mTc pertechnetate subtraction scintigraphy of the parathyroid gland performed in a study of 8 patients with clinical and biochemical evidence of hyperparathyroidism for diagnosis and localization of the lesion prior to sugery. 6 cases of parathyroid adenomas were accurately localized and 2 cases of diffuse hyperplasia associated with chronic renal failure(CRF) and multiple endocrine neoplasia(MEN) type I. 201Tl/99mTc pertechnetate scan was useful for patients with hyperparathyroidism, especially in definite localization preoperatively.