Recently 99mTc-Sestamibi (MIBI) has been introduced into parathyroid imaging. The purpose of this study was to evaluate the MIBI scan in an endemic goiter area. 25 patients with primary and 9 with secondary hyperparathyroidism (HPT) underwent a MIBI scan one day prior to surgical exploration of the neck. Cervicothoracic planar scintigraphy was performed 5, 15 and 120 min after i.v. injection of 444 MBq of 99mTc-Sestamibi. The MIBI scan correctly detected 20 of 25 adenomas in 25 patients with pHPT. In only 6 of 9 patients with parathyroid hyperplasia a focal uptake was found. The cause of one false-positive result in the control group was an increased MIBI uptake by a follicular adenoma of the thyroid. Parathyroid scintigraphy using 99mTc-Sestamibi as a single radiopharmaceutical is as sensitive in detecting and localizing parathyroid adenomas as the Tl/Tc-scintigraphy. Due to a high prevalence of thyroid adenomas in an endemic goiter area a higher rate of falsely positive results may be expected.