Background: The aetiology of CSX is still a matter of controversy and its relation to early atherosclerosis has not been fully investigated. Previous studies, however, have demonstrated impairment in normal endothelial function of the coronary microvasculature, resulting in inadequate coronary flow reserve as the major pathogenic mechanism. Carotid intima-media thickness (CIMT) measured by ultrasonography is a non-invasive test used to assess the presence of atherosclerosis and has been shown to be an independent predictor of future cardiovascular events. Aims: This study was performed to characterize the relation of carotid intima media thickness in patients with cardiac syndrome X compared to cardiac wise asymptomatic controls.Methods and results: We studied 25 consecutive CSX patients (mean age 52±5 years, 13 women) and 25 healthy controls (mean age 51±6 years, 10 women). The two groups were comparable for baseline clinical variable and coronary artery disease risk factors except for an increased incidence of hypertension (68% vs. 16%, P < 0.01), and diabetes mellitus (52% vs. 8%, P < 0.01) in patients with CSX compared to control group respectively. Common carotid IMT values were significantly higher in patients with CSX compared to controls (0.9 [0.55–1.78] vs. 0.61[0.46–1.16] mm, P<0.001). This difference remained significant even after exclusion of patients with hypertension and diabetes mellitus. Three patients in CSX group had carotid atherosclerotic plaques with none in the control group. Conclusions: This study showed that compared to control subjects, patients with CSX have increased mean common carotid artery IMT. The study demonstrated the usefulness of CIMT in predicting CSX patients. It raises the possibility that the pathogenesis of CSX may be an early form of atherosclerosis involving the coronary microvasculature.