The psychotogenic effects of psychostimulant drugs have provided a major line of evidence in support of the DA hypothesis of schizophrenia. To evaluate the effects of psychostimulant (PS) drug in schizophrenia and the clinical variables which may influence their expression, we reviewed 36 studies of PS drugs in patients with schizophrenia. Approximately 40% evidence a psychotogenic response to PS administration in doses that are subpsychotogenic in normals. Specific clinical variables appear to modify this response, including diagnosis, degree and type of psychopathology, stage of illness and pharmacologic status at the time of testing. Non-amphetamine-like PS drugs, e.g., methylphenidate, appear to have greater psychotogenic potency than amphetamine-like PS drugs. These results suggest the presence of a subgroup of schizophrenic patients who exhibit psychotic symptom activation with PS in a state dependent or independent fashion. This biologic phenomenon may be clinically exploitable and should be investigated further.