High-resolution magnetic resonance (MR) images of the neck were obtained in 23 patients with hyperparathyroidism. Surgical confirmation was available in all cases. MR imaging allowed accurate localization of 14 of 17 parathyroid adenomas, two of two parathyroid carcinomas, and five of eight hyperplastic glands, the latter from three patients. MR depicted nine of 11 (82%) abnormal glands that were 0.5-1.0 cm in size and 12 of 14 (85.7%) glands larger than 1 cm in diameter. In all but one case, abnormal glands had signal intensity greater than or equal to that of fat on spin-echo images with long repetition time and echo time. Parathyroid adenomas, carcinomas, and hyperplasia could not be distinguished from each other. The overall sensitivity and specificity of MR imaging in the detection of parathyroid abnormalities was 77.8% and 95.4% respectively, resulting in an accuracy of 90.2%. This compares favorably with other imaging modalities.