THIS ARTICLE EXAMINES BOTH TRADITIONAL AND CONTEMPORARY CONCEPTUALIZATIONS OF PROFESSIONAL CRIMINALS AS VIEWED BY CRIMINOLOGISTS. TRADITIONALLY, CRIMINOLOGISTS HAVE VIEWED PROFESSIONAL CRIMINALS AS BEING INVOLVED IN FULL-TIME, NONVIOLENT, HIGHLY SKILLED SPECIALTIES. CONTEMPORARY CONCEPTUALIZATIONS STRESS PROFESSIONAL CRIMINALS AS BEING NONSPECIALIZED, LESS SKILLED, AND INVOLVED IN VIOLENT BEHAVIOR. THESE CONCEPTUAL CHANGES REFLECT AN EMPHASIS UPON OBSERVATIONS RATHER THAN THEORETICAL DEVELOPMENTS AMONG CRIMINOLOGISTS EXAMINING PROFESSIONAL CRIME. AS LONG AS AN OBSERVATIONAL EMPHASIS PERSISTS, THEORIES CONCERNING PROFESSIONAL CRIMINALS WILL NOT PROGRESS EITHER RAPIDLY OR IN AN ORDERLY FASHION. CHANGING CONCEPTUALIZATIONS OF PROFESSIONAL CRIMINALS CAN BE VIEWED AS AN EXAMPLE OF INSUFFICIENT THEORETICAL DEVELOPMENT EXISTING WITHIN THE DISCIPLINE.(AUTHOR ABSTRACT)....BDS