Symptom development from birth to 12 years of age was examined in 18 children who met DSM-III criteria for schizophrenia with onset before 10 years of age. Using a follow-back design, symptom development was rated at each of four age levels using a DSM-III Symptom Rating Scale and the Achenbach Child Behavior Checklist. Results revealed a gradual developmental unfolding of a broad spectrum of symptoms affecting social, cognitive, sensory and motor functioning and beginning many years before the appearance of schizophrenic symptoms--usually in early infancy. Prior to 6 years of age, severe language deficits and motor development problems were each found in 72% of the sample and symptoms of infantile autism were found in 39% of the sample. Onset of schizophrenia occurred at an earlier age for children with a history of autistic symptoms during infancy than for other children in the sample. Schizophrenia as defined by DSM-III was entirely absent before 6 years of age.