Data are presented relating to 50 children whose weight at birth was 3 lb (1,360 gm) or less and who have now passed their fifth birthday, the statutory age for school entrance in Scotland. The findings follow. On individual intelligence testing 41% had scores of 90 or over, 40% had scores of 70 to 89, and 19% had scores of less than 70. Fifty-eight percent of children attended normal schools but one half of these required special treatment for educational retardation. Thirty percent were ineducable or required special schooling, primarily because of mental handicap, and 10% required special schooling because of physical handicap. One or more physical defects were detected in 52% of children; 42% had no physical defects or obvious mental retardation. No serious problems of behavior were reported for 42% of children. Of those with problems, restlessness and poor concentration were most commonly reported. Some factors affecting the incidence and survival of low weight infants were exammed with the following results. Multiple birth was over 20 times more common in this sample than in a general population of live births in Scotland. First born twins of very low weight were more likely to survive than second born twins. The marked preponderance of females in the survey sample was due to the increased chance of survival of female infants compared to males of like birth weight. Mothers giving birth to low weight infants were nearly twice as likely to show impaired reproductive capacity as mothers of maturely born infants. Mothers of low weight infants tended to be older than mothers in the general population, secondary to their tendency to have difficulty in conceiving. As compared with the general population, more low weight infants had fathers in the lower social classes. As compared with maturely born infants in Edinburgh, low weight infants were more likely to be reared in an unfavorable environment. Social and environmental differences were not very striking. Some factors affecting the outcome in infants of very low weight were examined with the following results. Females less often showed moderate or severe handicaps at 7 years or older than did males, and children from multiple births showed handicaps less often than singletons. Children reared in the best homes less often showed handicap than children reared in average or poor homes. However, compared by type of home with maturely born children, relative intellectual retardation was least marked in survey children from the poorest homes. Infants who had been markedly underweight for their gestation period were not at increased risk of later handicap. Severe complications of later pregnancy (but not complications of labor and delivery) were associated with a higher incidence of later handicap; males were particularly susceptible to the damaging effect of pregnancy complications. Abnormal postnatal signs more commonly followed a complicated than au uncomplicated pregnancy. More infants with abnormal signs showed later handicap. The incidence of moderate or severe handicap in children born from 1955 to 1959 was 56% compared with 32% of children of like birth weight born from 1948 to 1952. The survival rate has improved (from 17 to 30%) but there has been no improvement in later status of low weight infants.