The aim of this study was to prospectively evaluate the sensitivity, specificity and accuracy of fine-needle aspiration of thyroid nodules. From January 1978 to December 2003, 497 patients underwent fine-needle aspiration of thyroid nodules and then thyroidectomy. Fine-needle aspiration was performed with a fine 23-25 gauge and the aspirate was fixed and dyed with May-Grounwald-Giemsa method. The results of cytology were divided into four groups: positive for malignancy (77 patients), negative for malignancy (370 patients), suspect for malignancy (34 patients) and not diagnostic (16 patients). Suspect specimens also included follicular neoplasm and Hürthle cell neoplasm. Fine-needle aspiration results were compared with histopathologic analysis after thyroidectomy. There were 2 false-positive (0.5%) and 5 false-negative patients (1%). Sensitivity, specificity and accuracy were respectively 94.7%, 99% and 98.4%. This study confirms that fine-needle aspiration of thyroid nodules can be performed easily with high sensitivity, specificity and accuracy.