Dr. Ross will review research data on the complex relationship between psychological trauma, dissociation and psychosis. The overlap between dissociation and psychosis should be a focus of research, revisions of diagnostic criteria and daily clinical practice. Dissociative disorders should be a standard part of the differential diagnosis of psychotic disorders. For example, auditory hallucinations are the sole symptom criterion required for a DSM-IV diagnosis of schizophrenia, but voices are more characteristic of dissociative identity disorder than of schizophrenia, as are Schneiderian first-rank symptoms in general. Evidence will be presented suggesting that psychotic symptoms are often trauma-related rather than being due to endogenous biological abnormalities.