A key problem in schizophrenia research is how to assess the effects of treatment interventions given the spectrum of schizophrenia symptoms and patients' functioning. Measuring symptoms is complex, because these symptoms cover a wide variety of psychopathologic domains. The commonly recognized domains are the positive, negative, cognitive, excitement, and depression domains. This article critically reviews some of the available assessment tools of these domains together with other associated syndromes. The instruments discussed cover the broad range of psychopathology found in patients who have schizophrenia.