Training in general and forensic psychiatry in the assessment and treatment of sex offenders is in need of considerable improvement. Although most sex offenders are not mentally ill, many are subject to substance misuse, abnormal personality traits, personality disorder, learning disability or dysphoric mood, and in some organic factors will be involved. Comprehensive assessment of sex offenders includes a full history and mental state evaluation, obtaining a collateral history from other sources, observation, psychometric testing, and psychophysiological methods of assessment, including penile plethysmography. Trials of the use of the polygraph are also under way. The treatment of sex offenders, especially those with paraphilias, may include medication with selective serotonin reuptake inhibitors or anti-libidinal agents. Ethical considerations can be problematic, but a balance can often be found between the welfare of the offender and the safety of the public.