OBJECTIVE The authors' goal was to determine the prevalence of and risk factors for neuroleptic-induced movement disorders in a group of psychiatrically hospitalized children and adolescents. METHODS They evaluated the presence or absence of parkinsonism, tardive dyskinesia, and akathisia in 104 children and adolescents who were in residence in or admitted over a 6-month period to a state-operated child psychiatric center. They applied a standardized, structured assessment procedure used in research on adult and geriatric psychiatric patients and the mentally retarded. RESULTS The prevalence of parkinsonism among the 61 subjects at risk was 34% and was significantly associated with longer neuroleptic treatment periods immediately before evaluation. The prevalence of treatment-emergent tardive dyskinesia among the 41 subjects at risk was 12% and showed no association with quantitative neuroleptic treatment variables. However, patients with tardive dyskinesia were significantly more likely to have a family history of mental illness and significantly less likely to have a history of assaultive behavior. A pattern of complex pharmacological responses for parkinsonism and tardive dyskinesia, some of which are not typical of those most commonly reported in adults, was seen in this group of young patients. CONCLUSIONS The study data highlight the acute sensitivity of the neuroleptic-treated child and adolescent to the development of parkinsonism, the possible role of certain patient characteristics in the vulnerability to develop tardive dyskinesia, and the possibility that neuroleptic-induced side effects experienced by children and adolescents differ in some ways from those experienced by adults. The data further strongly support the need for systematic monitoring of neuroleptic-treated child and adolescent patients for a full range of side effects.