One would think that risk factors for transient ischemic attack (TIA) and asymptomatic carotid bruit (ACB) would be similar. In our referral population and in several previously reported cohort populations, however, men outnumber women among patients with TIA. In contrast, women outnumber men among patients with ACB. We found in two independent populations that women with ACB are up to 5.7 times less likely than men to have carotid stenosis. Thus women are more prone than men to have ACB, but their bruits much less commonly reflect carotid stenosis. Women are probably predisposed to have carotid bruit even in the absence of carotid stenosis. In our referral population of ACB, this tendency among women for carotid bruit without stenosis does not seem to be related to lower hematocrit, higher prevalence of heart murmur, constitutionally smaller carotid arteries, or differences in pulse rate or body habitus.