A randomized trial evaluated the effectiveness of moderate hypothermia (33.5°C for 72 hours) in infants with perinatal asphyxial encephalopathy. Infants under 6 hours of age with a gestational age of at least 36 weeks were randomly assigned to either intensive care plus cooling or intensive care alone. The primary outcome was death or severe neurodevelopmental disability at 18 months. Secondary outcomes included 12 neurologic and 14 other adverse outcomes. The study found no significant difference in the combined rate of death or severe disability between the cooled and noncooled groups (relative risk 0.86; 95% CI 0.68 to 1.07; P=0.17). However, cooling resulted in improved neurologic outcomes for survivors, including a higher rate of survival without neurologic abnormalities (relative risk 1.57; 95% CI 1.16 to 2.12; P=0.003), reduced risk of cerebral palsy (relative risk 0.67; 95% CI 0.47 to 0.96; P=0.03), and improved scores on the Mental Developmental Index and Psychomotor Developmental Index of the Bayley Scales of Infant Development II (P=0.03 for each) and the Gross Motor Function Classification System (P=0.01). Adverse events were mostly minor and not associated with cooling. The study concluded that moderate hypothermia did not significantly reduce the combined rate of death or severe disability but resulted in improved neurologic outcomes in survivors. The results suggest that while hypothermia may not significantly reduce mortality or severe disability, it may improve neurodevelopmental outcomes in some infants with perinatal asphyxial encephalopathy. The study was supported by grants from the U.K. Medical Research Council and the U.K. Department of Health. No potential conflicts of interest were reported.A randomized trial evaluated the effectiveness of moderate hypothermia (33.5°C for 72 hours) in infants with perinatal asphyxial encephalopathy. Infants under 6 hours of age with a gestational age of at least 36 weeks were randomly assigned to either intensive care plus cooling or intensive care alone. The primary outcome was death or severe neurodevelopmental disability at 18 months. Secondary outcomes included 12 neurologic and 14 other adverse outcomes. The study found no significant difference in the combined rate of death or severe disability between the cooled and noncooled groups (relative risk 0.86; 95% CI 0.68 to 1.07; P=0.17). However, cooling resulted in improved neurologic outcomes for survivors, including a higher rate of survival without neurologic abnormalities (relative risk 1.57; 95% CI 1.16 to 2.12; P=0.003), reduced risk of cerebral palsy (relative risk 0.67; 95% CI 0.47 to 0.96; P=0.03), and improved scores on the Mental Developmental Index and Psychomotor Developmental Index of the Bayley Scales of Infant Development II (P=0.03 for each) and the Gross Motor Function Classification System (P=0.01). Adverse events were mostly minor and not associated with cooling. The study concluded that moderate hypothermia did not significantly reduce the combined rate of death or severe disability but resulted in improved neurologic outcomes in survivors. The results suggest that while hypothermia may not significantly reduce mortality or severe disability, it may improve neurodevelopmental outcomes in some infants with perinatal asphyxial encephalopathy. The study was supported by grants from the U.K. Medical Research Council and the U.K. Department of Health. No potential conflicts of interest were reported.