Children and adolescents, ages 7 to 18 years, meeting DSM-IV criteria for schizophrenia, schizoaffective disorder and psychotic disorder not otherwise specified, with onset of psychosis before their 13th birthday, who have not responded to at least two prior trials with typical or a typical neuroleptics, will be eligible to participate in a double-blind, parallel group, trial of olanzapine-clozapine.