New revisions of diagnostic categories have produced the most recent classification systems, namely DSM-IV and ICD-10. The diagnostic approaches exemplified by these two nomenclatures are very similar to one another and represent a return to descriptive psychiatry in which careful observation of symptoms, signs, and course of mental diseases become the diagnostic criteria themselves. In many ways, these newest classification schemata can be considered a return to phenomenological psychiatry perhaps best exemplified at the start of this century by Emil Kraepelin. Thus, recent developments in psychiatric diagnosis can be thought of as "neo-Kraepelinian". Because they represent a relatively radical change from psychodynamic approaches to evaluation and diagnosis, they can also be called "revolutionary." This paper traces the roots of current diagnostic systems and compares and contrasts these systems to the classification schema described by Kraepelin. Diagnostic criteria for schizophrenia are used as an example of how diagnostic conventions have changed dramatically over the past 50 years. Discussion of the implications of this neo-Kraepelinian revolution in psychiatric diagnosis is included.