The benefits of obtaining a routine screening carotid duplex scan have not been established for patients with peripheral vascular disease but no signs or symptoms of carotid artery disease. We retrospectively reviewed all carotid duplex scans (4,000) performed at our institution between 1985 through 1989 and found for analysis 91 scans in 78 patients who underwent a screening duplex scan because of the presence of peripheral vascular disease. Patients with carotid bruits, abnormal carotid pulses, and focal or nonspecific neurologic symptoms were excluded. Thirty-three percent of these patients had carotid stenosis of 16% to 50%, 14% had carotid stenosis greater than or equal to 50%, and 5% had stenosis greater than or equal to 75%. Individual risk factors for atherosclerosis, including elderly age, coronary artery disease, hypertension, diabetes, smoking, and a recent or past history of cardiac or vascular surgery, did not predict the detection of high-grade carotid stenosis. However, all 11 of the patients with carotid stenosis greater than or equal to 50% were 68 years of age and older, and this age range, in combination with the various risk factors, increased the incidence of significant carotid artery stenosis (greater than or equal to 50%) to as high as 45%. We conclude that routine screening carotid duplex scan is indicated in elderly patients (age greater than or equal to 68 years) with peripheral vascular disease, even in the absence of any signs or symptoms of carotid artery disease, when other atherosclerotic risk factors are present.