Fifty-three cases with thyroid tumors (10 carcinomas, 16 adenomas and 27 nodular goiters) confirmed by operation and pathology were investigated by two-dimensional and color Doppler ultrasonography. The findings were as follows: malignant tumors usually had hypoechoes, indistinct and irregular margins, microcalcification, distal echo attenuation and arterial flow signals at the periphery as compared with benign tumors (P < 0.05). But differences in "halo" signs, degree of flow signals and interposed arterial vessels showed no statistical significance (P > 0.05). The clinical significance of high-velocity Doppler signals in the tumors and the pathologic basis of various sonographies of benign and malignant tumors are also discussed.