Renewed interest in surgical management of atherosclerotic disease of the carotid bifurcation underscores the necessity for accurate and efficacious means for diagnostic evaluation of patients with suspected carotid disease. Noninvasive testing by carotid duplex ultrasound, which combines high-resolution B-mode imaging with pulsed Doppler spectral analysis, is the method of choice. Noninvasive testing permits identification of potentially significant carotid stenosis, occlusion, or unstable plaque morphology with virtually no significant morbidity from the testing itself. Symptomatic patients, or patients with asymptomatic carotid bruits, can be evaluated serially to determine disease progression or response to medical management. In patients who are surgical candidates, substitution of noninvasive duplex ultrasound evaluation for carotid arteriography is controversial. Noninvasive testing is highly technique-dependent and probably requires at least 1 year of experience for acquisition of a sufficient "learning curve" for diagnostic reliability. This applies not only to the technical performance of the test but to interpretation of results. Proper training of technicians and quality assurance in individual vascular laboratories are crucial elements with respect to accuracy and reliability of results obtained in noninvasive testing.