[en] To assess the differential points between benign and malignant thyroid nodules, we retrospectively analysed the gray-scale and color Doppler ultrasovograms, radioisotope(RI) scans, and thyroid function tests of lO4 cases. The pathology of the lesion was confirmed as benign in 80 cases and malignant in 24 case, either at operation orby fine needle aspiration biopsy. Gray-scale ultrasonographic findings were analysed in terms of lymphadenopathy,size, and multiplicity. Color Doppler ultrasonography was performed in 40 case, and color singals were graded from type 0 to type III according to color flow distributions. There were no statistically significant differences inperipheral halo, size, multiplicity, color Doppler ultrasonograms, and findings at RI scan and thyriod functiontest between benign and malignant nodules(Chi-square test : P>0.05). However, internal punctate calcification,solid and hypoechoic pattern, cervical lymphadenopathy, irregular and illdefined outer margin, male gender weremore common in malignant thyroid nodules, while smooth and well-defined outer margin, complex echogenicity weremore common in benign nodules(P<0.05). Although color Doppler examination did not contribute to the differentialdiagnosis of benign and malignant nodules, complete halo in grat-scale ultrasonographt and color signal type II (prominent color flow at the periphery of the nodules; color 'halo' sihn) showed statistically significantcorrelation. In conclusion, gray-scale ultrasonography is a useful imaging modality for differential diagnosis of thyroid nodules, and further studies may be requires to clarify the availability of color Doppler ultrasonography