Background: Assessment of disease activity in patients with Takayasu’s arteritis(TA) is difficult due to absence of definitive tests. Presence of carotid intima-medial thickening has been suggested as a possible marker of inflammation and disease activity. Methods: We evaluated common carotid artery carotid intima-medial thickness(CCA-IMT) in 56 common carotid arteries(CCAs) in 28 healthy controls and 74 CCAs in 37 patients of TA.We correlated these findings with the presence of activity as assessed by the National Institutes of Health(NIH) cri- teria. Results: CCA-IMT was increased(>0.8 mm) in 59% of the patients with TA. In patients with disease activity, the CCA-IMT was more than in those without activity(1.5± 0.16 vs. 0.9± 0.2 mm, P< 0.005). This is presumably because of ongoing inflammation causing abnormal thickening. Even among patients without active disease, CCA-IMT was more than in controls(0.9± 0.2 vs. 0.6± 0.1 mm, P< 0.05) possibly due to a milder degree of inflammation or healing with fibrosis. All patients with angiographic carotid obstruction had increased CCA-IMT irrespective of whether they were active or not. However, in patients with angiographically normal carotid arteries, CCA-IMT was increased only among the patients who were active(1.4± 0.2 vs. 0.7± 0.04, P< 0.05). Abnormal CCA-IMT as marker of disease activity had a sensitivity of 82% and specificity of 60% . On excluding patients with increased CCA-IMT who had angiographic carotid stenosis(because the increase in CCA-IMT cannot be attributed entirely to activity alone in these patients), the specificity increased to 70% . Conclusion: Increased CCA-IMT is a reliable marker of active disease, especially in the absence of angiographically visible carotid disease. Background: Assessment of disease activity in patients with Takayasu’s arteritis (TA) is difficult due to absence of definitive tests. Presence of carotid intima-medial thickening has been suggested as a possible marker of inflammation and disease activity. Methods: We evaluated common carotid artery carotid intima-medial thickness (CCA-IMT) in 56 common carotid arteries (CCAs) in 28 healthy controls and 74 CCAs in 37 patients of TA.We correlated these findings with the presence of activity as assessed by the National Institutes of Health (NIH In patients with disease activity, the CCA-IMT was more than in those without activity (1.5 ± 0.16 vs. 0.9 ± 0.2 mm, P <0.005). This is presumably because of ongoing inflammation causing abnormal thickening. Even among patients without active disease, CCA-IMT was more than in controls (0.9 ± 0.2 vs. 0.6 ± 0.1 mm, P <0.05) possibly due to a milder degree of inflammation or healing with fibrosis. All patients with angiographic carotid obstruction had increased CCA-IMT irrespective of whether they were active or not. However, in patients with angiographically normal carotid arteries, CCA-IMT was increased only among patients who were active (1.4 ± 0.2 vs. 0.7 ± 0.04, P <0.05). Abnormal CCA-IMT as marker of disease activity had a sensitivity of 82% and specificity of 60%. On excluding patients with increased CCA-IMT who had angiographic carotid stenosis (because the increase in CCA-IMT can not be distributed locally to activity alone in these patients), the specificity increased to 70%. Conclusion: Increased CCA-IMT is a reliable marker of active disease, especially in the absence of angiographically visible carotid disease.