Metadiagnostic guidelines are delineated for evaluating the utility of both existing diagnostic criteria and recently proposed revisions (Magaro 1980). Among the metadiagnostic guidelines are the demonstration of differential treatment-outcome relationships for different disorders and the applicability of the characteristics of a superordinate diagnosis to its subordinate (or subtype) diagnoses. The authors note the conceptual development of the schizophrenia construct. Attempts to verify the existence of subtypes of schizophrenia in psychoanalytic theory, demographic traits, psychological assessment, and behavioral research are reviewed. Data accumulated from these efforts provide evidence regarding the validity of the distinction between paranoid and nonparanoid schizophrenia proposed by Magaro (1980). The authors conclude that a number of alternate relationships between paranoid and nonparanoid subtypes may by hypothesized. Only the notion that paranoid and nonparanoid subtypes are representative of differences in severity of schizophrenia may be rejected. As yet, little evidence exists for choosing one of the remaining alternatives as correct. Integrating research from diverse fields of study is advocated in the effort to refine conceptions of psychiatric disorders. In addition to continued attempts to make improvements in psychiatric diagnosis by changing the clinical symptoms used to define disorders, refinements may be accelerated by assessing the potential utility of other sources of information as the basis for psychiatric diagnosis. Performance on tasks employed in behavioral psychopathology research may represent such an example.