As of 1987, marked increases were reported by 33 States in the number of incarcerated sex offenders, with 55,000 individuals in State prisons. In some states, sex offenders represent one-third of the offender population. The increased rate is due to several factors: (1) increased public attention has led to increased reporting; (2) victim groups have been instrumental in changing the way victims are treated by the criminal justice system; (3) teachers and youth workers are much more aware of the possibility of sexual abuse; (4) many courts are handing out stiffer sentences; and (5) parole boards are becoming more reluctant to release sex offenders. Guidelines for treating incarcerated male sex offenders are organized in five parts. Part one addresses the psychodynamics of sex offenders (theories of sex offenses and characteristics and typologies of sex offenders). Part two considers treatment program implementation, administration, and evaluation. Part three specifically focuses on treatment such as clinical assessment, interpersonal skills, and behavioral techniques. Part four examines aftercare in terms of relapse prevention and community management. Part five discusses legal issues in the treatment of sex offenders (right to treatment, treatment modalities and consent, confidentiality, and liability). Appendixes present additional information on sex offender treatment programs and their evaluation. 46 references, 15 tables, 3 figures.