Increased accuracy of parathyroid hormone assays has yielded an earlier diagnosis of primary hyperparathyroidism, often in an asymptomatic stage. Non-invasive modalities used to localize parathyroid abnormalities have not been accurate for small adenomas. Although arteriography has been shown to be accurate in detection of adenomas, the invasive nature of the study, as well as possible complications, minimizes its use in preoperative localization of parathyroid abnormalities. The computed tomographic (CT) scan was used preoperatively in eight patients to assess its accuracy in localizing parathyroid abnormalities. The radiographic findings were correlated with surgical and pathologic findings. The conditions of seven patients were correctly diagnosed preoperatively by the CT scan, including that of one patient with diffuse hyperplasia. With the increased accuracy attained by this noninvasive examination, we believe that CT scanning should be a routine part of the preoperative examination of patients with primary hyperparathyroidism.