BACKGROUND: Birth before 26 weeks of gestation is associated with a high prev alence of neurologic and developmental disabilities in the infant during the fir st two years of life. METHODS: We studied at the time of early school age childr en who had been born at 25 or fewer completed weeks of gestation in the United K ingdom and Ireland in 1995. Each child had been evaluated at 30 months of age. T he children underwent standardized cognitive and neurologic assessments at six y ears of age. Disability was defined as severe (indicating dependence on caregive rs), moderate, or mild according to predetermined criteria. RESULTS: Of 308 surv iving children, 241 (78 percent) were assessed at a median age of six years and four months; 160 classmates delivered at full term served as a comparison group. Although the use of test reference norms showed that cognitive impairment (defi ned as results more than 2 SD below the mean) was present in 21 percent of the c hildren born extremely preterm (as compared with 1 percent in the standardized d ata), this value rose to 41 percent when the results were compared with those fo r their classmates. The rates of severe, moderate, and mild disability were 22 p ercent, 24 percent, and 34 percent, respectively; disabling cerebral palsy was p resent in 30 children (12 percent). Among children with severe disability at 30 months of age, 86 percent still had moderate to severe disability at 6 years of age. In contrast, other disabilities at the age of 30 months were poorly pre dictive of developmental problems at 6 years of age. CONCLUSIONS: Among extremel y preterm children, cognitive and neurologic impairment is common at school age. A comparison with their classroom peers indicates a level of impairment that is greater than is recognized with the use of standardized norms. BACKGROUND: Birth before 26 weeks of gestation is associated with a high prev alence of neurologic and developmental disabilities in the infant during the fir st two years of life. METHODS: We studied at the time of early school age childr en who had been born at 25 or fewer completed weeks of gestation in the United Kingdom and Ireland in 1995. Each child had been evaluated at 30 months of age. T he children underwent standardized cognitive and neurologic assessments at six y ears of age. Disability was defined as severe ( indicating dependence on caregive rs), moderate or mild according to the predetermined criteria. RESULTS: Of 308 surviving children, 241 (78 percent) were assessed at a median age of six years and four months; 160 classmates delivered at full term served as a comparison group. Although the use of test reference norms showed that cognitive impairment (defi ned as results more than 2 SD below the mean) was present in 21 percent of the c hildren was extremely preterm (a s compared with 1 percent in the standardized d ata), this value rose to 41 percent when the results were compared with those fo r their classmates. The rates of severe, moderate, and mild disability were 22 p ercent, 24 percent, and 34 percent, respectively; disabling cerebral palsy was p resent in 30 children (12 percent). Children with severe disability at 30 months of age, 86 percent still had moderate to severe disability at 6 years of age. at the age of 30 months were poorly pre dictive of developmental problems at 6 years of age. CONCLUSIONS: Among extremel y preterm children, cognitive and neurologic impairment is common at school age. A comparison with their classroom peers indicates a level of impairment that is greater than is recognized with the use of standardized norms.