Field supervision of probationers and parolees is based primarily on a 'caseworker' modality. The most common methods of therapy in probation include vocational counseling, group and individual psychotherapy, and drug rehabilitation. These treatment modalities seem to focus on engendering a positive self-concept in the probationer and counteracting low self-esteem and diminished self-confidence. Large caseloads make such intensive treatment difficult. The provision of effective services is further complicated by officers' being inadequately trained for their casework functions. The use of outside mental health services by probation and parole staff varies tremendously across jurisdictions. Availability of 'schemas,' or categories, guides the processing of case information and controls the formulation of supervisory strategies and the selection of treatment modalities. To the extent that these schemes are valid, they offer an efficient way of handling parts of a caseload and a nucleus for the future classification of parolees. Central to the diagnostic process is the imputation of a cause -- a mechanism or 'problem' -- that interprets an offender's life and answers questions about why a crime has occurred. The effort to rehabilitate offenders faces an uphill battle. In addition to severe resource constraints and the lack of demonstrably successful techniques, well-intentioned programs may have consequences that undermine their own goals, such as absence of voluntary treatment. Forty-eight references are listed.