Schizophrenia has been linked with childhood psychological abnormalities since it was first described, but studies of associations have not used population samples and so may be subject to bias. We have studied associations between adult-onset schizophrenia and childhood sociodemographic, neurodevelopmental, cognitive, and behavioural factors within a cohort of 5362 people born in the week March 3-9, 1946. Childhood data were gathered prospectively and case ascertainment was independent of routine follow-up of this cohort. 30 cases of schizophrenia arose between ages 16 and 43 years (cumulative risk 0.63% [95% CI 0.41-0.86%]). Milestones of motor development were reached later in cases than in controls, particularly walking (difference in means 1.2 months [0.1-2.3], p = 0.005), and up to age 15, cases had more speech problems than had controls (odds ratio 2.8 [0.9-7.8], p = 0.04). Low educational test scores at ages 8, 11, and 15 years were a risk factor, with significant linear trends across population distributions; risk was not confined to very low scores. Solitary play preference at ages 4 and 6 years predicted schizophrenia (odds ratios 2.1, 2.5, p = 0.05). At 13 years cases rated themselves as less socially confident (p for trend, 0.04). At 15 years, teachers rated cases as being more anxious in social situations (p for trend 0.003), independent of intelligence quotient. A health visitor's rating of the mother as having below average mothering skills and understanding of her child at age 4 years was a predictor of schizophrenia in that child (odds ratio 5.8 [0.8-31.8], p = 0.02). Differences between children destined to develop schizophrenia as adults and the general population were found across a range of developmental domains. As with some other adult illnesses, the origins of schizophrenia may be found in early life.