BACKGROUND We retrospectively studied whether ultrasound-guided fine-needle aspiration biopsy (US-FNAB) showed improved sensitivity in patients with palpable thyroid nodules. METHODS A total of 70 patients (72 lesions) with thyroid nodules underwent US-FNAB and 94 patients (94 lesions) underwent FNAB guided by manual palpation (standard FNAB). The diagnoses obtained by US-FNAB were compared with the surgical findings. RESULTS The sensitivity of US-FNAB for palpable thyroid nodules was 62% the specificity was 74% the accuracy was 68% the positive predictive value was 100%, the negative predictive value was 70% and the inadequate biopsy rate was 17%. In contrast, the sensitivity of standard FNAB was 45%, the specificity was 51%, the accuracy was 48% the positive predictive value was 96, the negative predictive value was 55, and the inadequate biopsy rate was 30%. The accuracy of US-FNAB was significantly higher than that of standard FNAB. For tumors < or = 2 cm in diameter, the sensitivity and accuracy of US-FNAB were both significantly higher than those of standard FNAB. CONCLUSIONS These findings suggest that US-FNAB can improve the preoperative diagnosis of thyroid cancer, especially in patients with tumors < or = 2 cm in diameter.