A major problem in evaluating the effectiveness of sex offender treatment is the absence of standardized techniques generally accepted by researchers as reliable and valid measures of the frequency or nature of deviant sexual practices. Aside from clinical judgments, self-reports, reports by significant others, arrest records, and plethysmography (the measure of erectile responses to sexual stimuli), few assessment strategies have been attempted. Regarding treatment techniques, the biological techniques found to be most promising are two types of antiandrogen hormone therapy: medroxyprogesterone acetate and cyproterone acetate. Such therapy has reduced an offender's sex drive while the hormones are in the system. Promising behavioral techniques designed to eliminate inappropriate sexual behavior include aversion therapy and covert sensitization. Behavioral treatments designed to increase nondeviant sexual behavior include fantasy modification. Areas for future research encompass the correlates of long-lasting effects after treatment termination and the mechanisms and action sites of antiandrogens. 81 references.