The accuracy of clinical diagnosis and fine-needle aspiration biopsy (FNAB) was evaluated in 169 patients surgically treated for nodular thyroid disease. Patients were divided into three groups with high, moderate, or low suspicion of malignant neoplasms on clinical grounds without previous knowledge of cytologic or histologic results. Histologic examination revealed an overall malignant neoplasm rate of 23%; the rate was 71%, 14%, and 11% for the groups with high, moderate, and low suspicion, respectively. The FNAB diagnostic interpretations of malignant and uncertain were considered positive. Overall sensitivity, specificity, and accuracy for FNAB were 92%, 71%, and 75%, respectively. Sensitivity in the high-, moderate-, and low-suspicion groups was 95%, 89%, and 88%, respectively; specificity was 88%, 72%, and 67%, respectively; and accuracy was 93%, 75%, and 69%, respectively. In our opinion, all patients in the group with high clinical suspicion need surgical treatment whatever the FNAB result; those with lower degrees of clinical suspicion and malignant or uncertain FNAB result [corrected] should also undergo surgery.