To describe the clinical profile of Asian Indian patients with Takayasu's arteritis (TAK) and to compare clinical features and outcome of childhood-onset Takayasu's arteritis (cTAK) with adult-onset TAK (aTAK).Data related to clinical features and response to treatment of patients with cTAK (age of onset <16 years) and aTAK from a large observational cohort in our tertiary care teaching hospital were noted and compared.Altogether, 602 patients (cTAK = 119; aTAK = 483) were studied. Patients with cTAK had a blunted female: male ratio; but fever, elevated acute phase reactants, involvement of abdominal aorta or its branches, hypertension, abdominal pain, elevated serum creatinine and cardiomyopathy were more common in cTAK as compared with aTAK. Patients with aTAK were more likely to have aortic-arch disease and claudication than cTAK. During follow-up, complete remission was more common in cTAK (87% vs 66%; P < 0.01), but subsequent relapses were equally common (30% vs 27%; P = 0.63). Independent associations of disease duration at presentation with disease extent [Disease Extent Index in TAK (DEI.Tak)] and damage [TAK Damage Score (TADS)] were observed (P ≤ 0.01). Moreover, 54% of patients with symptom duration of >5 years at presentation still continued to have elevated CRP suggesting continued and active inflammation warranting escalation or inititation of immunosuppression.Patients with cTAK are more likely to have arterial disease below the diaphragm, systemic inflammation and achieve remission. Disease of the aortic arch is more common in patients with aTAK. Longer duration of symptoms prior to initiation of immunosuppression, thereby leading to extensive disease and damage, reflects ongoing disease activity as the rule rather than exception in untreated TAK.