Between October 1994 and October 1998, 110 consecutive patients with biochemically proven primary hyperparathyroidism who were to undergo surgery were enrolled in this study. Ultrasound and spiral CT were routinely performed as standard preoperative imaging modalities in the first series of 65 patients. In the second series of 45 patients, ultrasound was performed as the sole initial modality; it was supplemented by CT only in case of inconclusive test results