In this international evaluator-blinded, randomized, controlled, equivalence trial, researchers recruited infants born at more than 26 gestational weeks and less than 60 gestational weeks and who had undergone inguinal hernia repair from 28 hospitals in Australia, Italy, the United States, the United Kingdom, Canada, the Netherlands, and New Zealand. These infants were randomly assigned (1:1) to receive either conscious local anesthesia or sevoflurane general anesthesia. Network-based randomization was completed in two or four blocks and stratified by birth location and gestational age. These infants were excluded if they had risk factors for neurological injury. The primary outcome of the study will be the Wechsler Preschooler Intelligence Scale, Third Edition (WPPSI-III) full scale IQ score at age 5 years. The secondary outcome will be the Bayley Scales of Infant and Toddler Development III composite cognitive score assessed at age 2 years. The analysis was adjusted for gestational age at birth for each protocol. A mean five-point (1/3 SD) difference was predefined as a clinical equivalence boundary. Between February 9, 2007, and January 31, 2013, 363 infants received awake local anesthesia and 359 infants received general anesthesia. Outcome data were available for 238 infants in the awake local anesthesia and 294 infants in the general anesthesia group. In analyses by per-protocol, the cognitive composite score (mean [SD]) was 98.6 (14.2) in the awake local anesthesia group and 98.2 (14.7) in the general anesthesia group. The means between groups were equal (0.169 for awake local anesthesia minus general anesthesia and 2.30 2.64 for 95% Cl). The median time for the general anesthesia group was 54 minutes. For this secondary outcome, the researchers did not find any evidence that sevoflurane anesthesia, which takes less than 1 hour in infancy, increases the risk of adverse neurodevelopmental outcomes at 2 years of age compared with local anesthesia.