BACKGROUND: Birth before 26 weeks of gestation is associated with a high preva lence of neurologic and developmental disabilities in the infant during the firs t two years of life. METHODS: We studied at the time of early school age childre n who had been born at 25 or fewer completed weeks of gestation in the United Ki ngdom and Ireland in 1995.Each child had been evaluated at 30 months of age. The children underwen t standardized cognitive and neurologic assessments at six years of age. Disabil ity was defined as severe (indicating dependence on caregivers), moderate, or mi ld according to predetermined criteria. RESULTS: Of 308 surviving children, 241 (78 percent) were assessed at a median age of six years and four months; 160 cla ssmates delivered at full term served as a comparison group. Although the use of test reference norms showed that cognitive impairment (de-fined as results mor e than 2 SD below the mean) was present in 21 percent of the children born extre mely preterm (as compared with 1 percent in the standardized data), this value r ose to 41 percent when the results were compared with those for their classmates . The rates of severe, moderate, and mild disability were 22 percent, 24 percent , and 34 percent, respectively; disabling cerebral palsy was present in 30 child ren (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 predictive of developme ntal problems at 6 years of age. CONCLUSIONS: Among extremely preterm children, cognitive and neurologic impairment is common at school age. A comparison with t heir classroom peers indicates a level of impairment that is greater than is rec ognized with the use of standardized norms. BACKGROUND: Birth before 26 weeks of gestation is associated with a high prevalence of neurologic and developmental disabilities in the infant during the firs t two years of life. METHODS: We studied at the time of early school age childre n who had been born at 25 or fewer completed weeks of gestation in the United Ki ngdom and Ireland in 1995.Each child had been evaluated at 30 months of age. The children underwen t standardized cognitive and neurological assessments at six years of age. Disabil ity was defined as severe ( indicating dependence on caregivers), moderate or mi ld 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 cla ssmates delivered at full term served as a comparison group. Although the use of test reference norms showed that cognitive impairment (de-fined as results mor e than 2 SD below the mean) was present in 21 percent of the children born extre mely preterm (a s compared with 1 percent in the standardized data), this value r ose to 41 percent when the results were compared with those for their classmates. The rates of severe, moderate, and mild disability were 22 percent, 24 percent, and 34 percent, each; disabling cerebral palsy was present in 30 child ren (12 percent). Children with severe disability at 30 months of age, 86 percent still had moderate-to-severe disability at 6 years of age. age of 30 months were poorly predictive of developme ntal problems at 6 years of age. CONCLUSIONS: Among extremely preterm children, cognitive and neurologic impairment is common at school age. A comparison with t heir classroom peers indicates a level of impairment that is greater than is recognized with the use of standardized norms.