The survival rate of infants born alive between 24 and 28 weeks of gestation has increased significantly in this tertiary care centre, from about 9% in the first cohort studied (1966-1970), to 19.5% in the second cohort (1971-1974) and 50.3% in the third cohort (1977-1982); the borderline of practical viability decreased from 27 to 24 weeks over the years of the study. The number of mothers with a history of prior termination of pregnancy increased about sixfold from the second to the third cohorts but the rate of premature births increased by only 50%. The augmented survival rate was accompanied by an increase in the prevalence and total number of children with cerebral palsy, but bilateral blindness due to retinopathy of prematurity and severe sensorineural deafness were reduced. When 96% of children in the third cohort were assessed at two years of age. 13% had severe handicaps, 59% were considered normal and in 24% some handicap was suspected. The serious handicap rate was 28% for children born at 24-26 weeks compared with 8.5% for those born at 27-28 weeks of gestation.