The author demonstrates that specific data and research needs require the attention of criminal justice system students, scholars, and practitioners. He contends that the criminal justice system does not necessarily function as a system. The following concepts are discussed: variance in criminal justice, external validity, formal versus informal justice, the need for criminal justice research, and a systems approach to criminal justice information. The author suggests that national and statewide information systems be implemented to meet the data needs of criminal justice researchers and practitioners. The design of such a system should incorporate a standardized data set on the individual and on the criminal justice system. This data set should be defined by a team of researchers and practitioners and should include an optional section to allow criminal justice agency data needs or temporary research needs to be addressed without disrupting the collection of standardized data. Types of data to be included in an information system are identified, and criteria for making criminal justice research comparisons are listed. 37 references