Five alternative sets of diagnostic criteria for schizophrenia and related psychotic disorders are presented in the appendix following this report. They include the DSM-III-R criteria, the most recent version of the ICD-10 research criteria, and three new sets that have been proposed as options for DSM-IV. A multicenter field trial is currently gathering data that will allow researchers to compare the performance characteristics of each set of criteria, including dimensions such as classification rates, reliability, and user-friendliness. In this report, the rationale behind the proposed modifications and the methods and goals of the field trials are summarized.