To assess the accuracy of high-resolution sonography of the parathyroid glands, a consecutive series of sonograms in 58 patients was reviewed. The study population was limited to patients thought clinically to have primary hyperparathyroidism and likely to have one enlarged adenomatous gland. Patients with renal failure or other evidence of secondary hyperparathyroidism were excluded. Typical sonographic features of parathyroid adenoma were observed. An overall accuracy of 92% was obtained for the identification of surgically confirmed parathyroid gland enlargement due to adenoma.