One hundred carotid arteries were investigated with both Duplex and DSA.The accuracy of Duplex was acceptable.Systolic peak frequency and the appearance of spectral broadening were used toanalyse the Doppler spectrum.The sensitivity,and specificity were satisfactory to identify internal carotidstenosis particularly critical stenosis.The results show that duplex scanning is a reliable noninvasive ex-amination method for internal carotid stenosis.