Large population-based studies indicate that children who will as adults develop the clinical syndrome of schizophrenia are different from their peers in terms of the acquisition of a range of neurological, cognitive and behavioural characteristics. These studies are also identifying possible causal factors which might operate early in life and so be responsible for a longitudinal aspect of the disorder. Studies of the brain yield results consistent with the multi-system nature of the clinical syndrome of schizophrenia in adult life, and with the notion of a longitudinal or developmental phenotype, of which the adult syndrome is but one aspect. Work in these areas is reviewed with special reference to national birth cohorts from Britain and Finland.