Stability of schizophrenia diagnosis from adolescence to adulthood, antecedents of schizophrenia, and differences in developmental and behavioural histories between subjects with early onset schizophrenia (EOS) and with adult onset schizophrenia (AOS) were investigated in 145 adult subjects diagnosed with mental disorders in adolescence and re-diagnosed on the basis of medical records according to DSM-IV.A very high diagnostic stability schizophrenia was demonstrated at the 28-year follow-up. Several factors, including neurological adversities, delayed language development, low IQ, and congenital functional disability, differentiated significantly between schizophrenic subjects and non-schizophrenic subjects. Histories of concussion, physical abuse, parental divorce, and unstable familial context differentiated significantly between EOS and AOS subjects. Our findings support earlier evidence of schizophrenia being a chronic disorder with high diagnostic stability, and confirm the importance of neurological adversities, delayed language development, and low IQ as factors predictive of schizophrenia. Exploration of four case histories of AOS subjects delineates "pre-schizophrenic warning cluster" where combination of neurological adversities, temperamental problems, antisocial behaviour, preference for solitary play, and unstable family system constitute main factors.