Hyperglycemia during acute ischemic stroke is common and is associated with worse outcomes. The efficacy of intensive treatment of hyperglycemia in this setting remains unknown.To determine the efficacy of intensive treatment of hyperglycemia during acute ischemic stroke.The Stroke Hyperglycemia Insulin Network Effort (SHINE) randomized clinical trial included adult patients with hyperglycemia (glucose concentration of >110 mg/dL if had diabetes or ≥150 mg/dL if did not have diabetes) and acute ischemic stroke who were enrolled within 12 hours from stroke onset at 63 US sites between April 2012 and August 2018; follow-up ended in November 2018. The trial included 1151 patients who met eligibility criteria.Patients were randomized to receive continuous intravenous insulin using a computerized decision support tool (target blood glucose concentration of 80-130 mg/dL [4.4-7.2 mmol/L]; intensive treatment group: n = 581) or insulin on a sliding scale that was administered subcutaneously (target blood glucose concentration of 80-179 mg/dL [4.4-9.9 mmol/L]; standard treatment group: n = 570) for up to 72 hours.The primary efficacy outcome was the proportion of patients with a favorable outcome based on the 90-day modified Rankin Scale score (a global stroke disability scale ranging from 0 [no symptoms or completely recovered] to 6 [death]) that was adjusted for baseline stroke severity.Among 1151 patients who were randomized (mean age, 66 years [SD, 13.1 years]; 529 [46%] women, 920 [80%] with diabetes), 1118 (97%) completed the trial. Enrollment was stopped for futility based on prespecified interim analysis criteria. During treatment, the mean blood glucose level was 118 mg/dL (6.6 mmol/L) in the intensive treatment group and 179 mg/dL (9.9 mmol/L) in the standard treatment group. A favorable outcome occurred in 119 of 581 patients (20.5%) in the intensive treatment group and in 123 of 570 patients (21.6%) in the standard treatment group (adjusted relative risk, 0.97 [95% CI, 0.87 to 1.08], P = .55; unadjusted risk difference, -0.83% [95% CI, -5.72% to 4.06%]). Treatment was stopped early for hypoglycemia or other adverse events in 65 of 581 patients (11.2%) in the intensive treatment group and in 18 of 570 patients (3.2%) in the standard treatment group. Severe hypoglycemia occurred only among patients in the intensive treatment group (15/581 [2.6%]; risk difference, 2.58% [95% CI, 1.29% to 3.87%]).Among patients with acute ischemic stroke and hyperglycemia, treatment with intensive vs standard glucose control for up to 72 hours did not result in a significant difference in favorable functional outcome at 90 days. These findings do not support using intensive glucose control in this setting.ClinicalTrials.gov Identifier: NCT01369069.