BACKGROUND: Fine-needle aspiration biopsy is the standard diagnostic test for evaluating possible malignancy in a thyroid nodule. OBJECTIVE: To evaluate the role of routine ultrasonography in the management of nodular thyroid disease. DESIGN: Retrospective chart review. SETTING: Multidisciplinary thyroid nodule clinic (endocrinology and radiology). PATIENTS: Patients with suspected nodular thyroid disease or suspected recurrent thyroid cancer referred between October 1995 and March 1997. All patients had thyroid ultrasonography and ultrasonography-guided fine-needle aspiration biopsy of nodules at least 1 cm in maximum diameter. MEASUREMENTS: Medical records, ultrasonography findings, cytology reports, and histologic reports were reviewed. Ultrasonography findings were compared with the referring physician's findings on physical examination. RESULTS: 223 patients were seen in the clinic. A total of 209 fine-needle aspiration biopsies were performed on 156 patients. Among 50 of 114 patients referred for a solitary nodule, ultrasonography detected additional nonpalpable nodules at least 1 cm in diameter in 27 and determined that no nodules required aspiration in 23. Of 59 patients referred for a diffuse goiter or a multinodular gland, ultrasonography detected discrete nodules at least 1 cm in diameter that required aspiration in 39 and determined that aspiration was unnecessary in 20. CONCLUSIONS: Ultrasonography altered the clinical management for 63% of the patients (109 of 173) referred to the thyroid nodule clinic after abnormal results on thyroid physical examination.