All surviving babies of less than 32 weeks' gestation born to mothers resident in the Northern region in 1983 were assessed. No baby was lost to follow up, and 230 long term survivors were assessed when 2 years old, by a single observer. Among 248 neonatal survivors, severe disability was present in 10 of the 37 at 24-27 weeks' gestation (27%) and in 18 of the 211 at 28-31 weeks' gestation (9%). On average the surviving babies required 27 days and seven days of intensive care nursing respectively. Babies who were ventilated for more than two weeks and babies who had neonatal fits had a poor prognosis. Because of postneonatal deaths only 20 of the 230 long term survivors of less than 32 weeks' gestation were severely disabled (9%). Comparable data were obtained for all babies weighing 1500 g or less at birth, irrespective of their gestational age. Severe disability was seen in eight of the 49 neonatal survivors (16%) who had weighed 500-999 g at birth, and in 17 of the 171 survivors (10%) who had weighed 1000-1499 g. The 10 neonatal survivors who had weighed exactly 1500 g at birth were all well. Only 18 of the 212 long term survivors (8%) who had weighed 1500 g or less at birth were severely disabled. Because the period of gestation is the only variable known to the obstetrician before delivery, and disability correlates better with gestation than birth weight, future studies should concentrate on relating morbidity, mortality, and the cost of neonatal care to gestation rather than weight at birth.