Subjective and objective classification systems are compared, elements of an objective classification system are examined, and lessons from classification research are noted. It is pointed out that classification systems vary in terms of the factors or variables considered in classifying inmates and the points or weights assigned to each factor. Although prior history and disciplinary adjustment are among the most commonly used predictive criteria in initial classification, no research has considered the reliability of these variables. Only preincarceration variables have been tested, and aside from the weak but consistent predictors of age, marital status, and race, such variables are the least likely to have predictive value. Overall, the ability to predict inmate or offender behavior is limited. 18 references. (Author abstract modified)