Classification has not yet delivered on its promise as a treatment and corrections management tool, although a number of classification taxonomies and systems have been developed. The problem has been one of inertia rather than the absence of guidelines. Good classification systems should offer sufficient flexibility to classify all inmates, offer clear operational definitions, provide reliability and internal validity, reflect status changes, match inmates with intervention approaches, and offer the opportunity for economic administration. The system should not exclude inmates from any services and should collect data from a range of sources. Currently, two systems are being assessed: one based on the Minnesota Multiphasic Personality Inventory and another based on the 16 - Personality Factor questionnaire. Recently, judges have come to view classification deficiencies as heavily implicated in the fostering of other prison inadequacies, and the courts have found relationships between classification and general prison deficiencies. Inmate rights suits have mentioned misleading or inefficient systems. Classification error is also related to overcrowding. Notes, 21 references, and 7 case citations are included. Appendices provide classification guidelines which include additional references.