['The role of noninvasive methods in the evaluation of collateral circulation has yet to be defined. We hypothesized that a favorable pattern of leptomeningeal collaterals, as identified by CT angiography, correlates with improved outcomes.', 'Data from a prospective cohort study at 2 university-based hospitals where CT angiography was systematically performed in the acute phase of ischemic stroke were analyzed. Patients with complete occlusion of the intracranial internal carotid artery and/or the middle cerebral artery (M1 or M2 segments) were selected. The leptomeningeal collateral pattern was graded as a 3-category ordinal variable (less, equal, or greater than the unaffected contralateral hemisphere). Univariate and multivariate analyses were performed to define the independent predictors of good outcome at 6 months (modified Rankin Scale score ≤2).', 'One hundred ninety-six patients were selected. The mean age was 69±17 years and the median National Institute of Health Stroke Scale score was 13 (interquartile range, 6 to 17). In the univariate analysis, age, baseline National Institute of Health Stroke Scale score, prestroke modified Rankin Scale score, Alberta Stroke Programme Early CT score, admission blood glucose, history of hypertension, coronary artery disease, congestive heart failure, atrial fibrillation, site of occlusion, and collateral pattern were predictors of outcome. In the multivariate analysis, age (OR, 0.95; 95% CI, 0.93 to 0.98; P=0.001), baseline National Institute of Health Stroke Scale (OR, 0.75; 0.69 to 0.83; P<0.001), prestroke modified Rankin Scale score (OR, 0.41; 0.22 to 0.76; P=0.01), intravenous recombinant tissue plasminogen activator (OR, 4.92; 1.83 to 13.25; P=0.01), diabetes (OR, 0.31; 0.01 to 0.98; P=0.046), and leptomeningeal collaterals (OR, 1.93; 1.06 to 3.34; P=0.03) were identified as independent predictors of good outcome.'] Is the pattern of leptomeningeal collaterals on CT angiography a strong predictor of long-term functional outcome in stroke patients with large vessel intracranial occlusion?