OBJECTIVE: This study sought to determine whether affective abnormalities could be detected in home movies of children who later developed schizophrenia. METHOD: Trained observers coded facial expressions of emotion of 32 schizophrenic patients and 31 of their healthy siblings from home movies made when they were children. All of the patients met the DSM-III criteria for schizophrenia with onset in late adolescence or early adulthood. The sibling comparison subjects had no history of psychiatric illness. Nine emotions and a neutral category were rated. RESULTS: Analyses revealed significantly lower proportions of joy expressions among the total expressions of the preschizophrenic female subjects than among the same-sex healthy siblings. This difference extended from infancy through adolescence. Among the male subjects, there were inconsistent differences between diagnostic groups in expressions of joy across age levels. However, both the preschizophrenic male subjects and the preschizophrenic female subjects showed greater negative affect than their same-sex comparison groups. CONCLUSIONS: These findings lend support to the assumption that vulnerability to schizophrenia may be subtly manifested in emotional behavior long before the onset of clinical symptoms.