The aim of the study was to evaluate the role of neck ultrasonography in follow-up of patients with differentiated thyroid cancer. Sixty-three patients had total thyroidectomy and 131I ablation for differentiated thyroid cancer and had a negative whole body scan during follow-up. They were admitted for a high resolution neck ultrasound examination. Sixteen of 63 patients presented images suspicious for lymph node metastasis and/or for local recurrences (4 cases). Fine needle aspiration confirmed the suspicion of malignancy in 12 patients: only lymph node metastasis in 8 cases, local recurrence and lymph node metastasis in 3 cases, and in one case only local recurrence. Fine needle aspiration was suspicious for lymphadenitis in 4 cases. Thyroglobulin levels were very high in all patients with local recurrence and/or lymph node metastasis but undetectable in 2 cases presenting node metastasis and in 4 cases with lymphadenitis. All but one patient were admitted for surgery and the cytological diagnosis was confirmed. Early identification of a pathologic mass in the neck is a desirable goal; high resolution echography can play an important role in the follow-up of these patients and can detect local recurrences even when there is a negative whole body scan or undetectable thyroglobulin level.