Often patients with personality and affective disorder are troubled by psychotic and psychotic-like symptoms. Predicting a course that includes such symptoms, and subsequently adjusting treatment to take into consideration the added difficulties presented by psychosis, is clinically important. In the current study, a measure of thought disorder, the Thought Disorder Index (TDI), significantly predicted prospective psychotic and psychoticlike symptoms in a sample of 49 personality and affective disorder patients. Multiple regressions demonstrated that the TDI had predictive value above and beyond that of a clinical interview. The high prevalence of psychotic symptoms was most striking in patients with borderline personality disorder.