The factors include sexual history and preference, substance abuse, mental illness, personality and defensiveness, history of violence, neuropsychological impairment, and biological problems. Once information has been collected on these factors, a treatment plan can be developed and risk to the community can be evaluated. Individuals who appear to have paraphilic sexual preferences should be treated differently from those who do not. In the case of incest offenders, for example, only 25 percent have an erotic preference for children. Substance abuse also appears to interfere with other behavioral changes. The cooperativeness or ability of an individual to focus on therapy issues, for example, may be hindered by drunkenness. The reliability and validity of existing measures to assess paraphilics and sex offenders are reviewed, and measures that offer some index of dangerousness and targets for treatment are suggested. 88 references and 2 tables