The diagnostic accuracy of 5 MHz continuous-wave (C-W) Doppler with spectral analysis for detecting carotid bifurcation disease was evaluated. In a first phase of the study, normal confidence intervals for peak frequency data and spectrum width were established and Doppler spectrum abnormalities were separated into three types (spectral broadening with preserved window, spectral broadening without window, sequence of abnormalities including inverted Doppler spectrum). In a second phase the diagnostic accuracy of these variables was tested on 86 carotid arteries as independently compared with angiography. Whereas both peak frequency data and spectrum distribution findings were invariably abnormal in stenoses greater than or equal to 60%, spectrum distribution findings were more accurate in 30-59% stenosis. Using spectrum distribution criteria, sensitivity and specificity for stenosis greater than or equal to 30% were 94.6% and 90.7% respectively. All variables were insensitive for stenoses less than 30% lumen diameter reduction.