Characterization of patients with both psychotic and mood symptoms, either concurrently or at different points during their illness, has always posed a nosological challenge and this is reflected in the poor reliability, low diagnostic stability, and questionable validity of DSM-IV Schizoaffective Disorder. The clinical reality of the frequent co-occurrence of psychosis and Mood Episodes has also resulted in over-utilization of a diagnostic category that was originally intended to only rarely be needed. In the Diagnostic and Statistical Manual of Mental Disorders, fifth edition, an effort is made to improve reliability of this condition by providing more specific criteria and the concept of Schizoaffective Disorder shifts from an episode diagnosis in DSM-IV to a life-course of the illness in DSM-5. When psychotic symptoms occur exclusively during a Mood Episode, DSM-5 indicates that the diagnosis is the appropriate Mood Disorder with Psychotic Features, but when such a psychotic condition includes at least a two-week period of psychosis without prominent mood symptoms, the diagnosis may be either Schizoaffective Disorder or Schizophrenia. In the DSM-5, the diagnosis of Schizoaffective Disorder can be made only if full Mood Disorder episodes have been present for the majority of the total active and residual course of illness, from the onset of psychotic symptoms up until the current diagnosis. In earlier DSM versions the boundary between Schizophrenia and Schizoaffective Disorder was only qualitatively defined, leading to poor reliability. This change will provide a clearer separation between Schizophrenia with mood symptoms from Schizoaffective Disorder and will also likely reduce rates of diagnosis of Schizoaffective Disorder while increasing the stability of this diagnosis once made.