Data are reported on the sexual behavior of 39 released sex offenders who agreed voluntarily to surgical castration while imprisoned in West Germany. Findings indicated that frequency of coitus, masturbation, and sexual thoughts are seen as strongly reduced after castration. Sexual desire and sexual arousability are perceived by the subjects as having been considerably impaired by castration. In comparison with other studies, however, it was shown that male sexual capacity was not extinguished soon after castration. Particularly noteworthy is that 11 of 35 castrates (31%) stated they were still able to engage in sexual intercourse. Rapists proved to be sexually more active after castration than homosexuals or pedophiliacs. There seems to be a strong effect on sexual behavior only if castration is performed on males between the age of 46 and 59 years. In general, the findings do not justify recommending surgical castration as a reliable treatment for incarcerated sex offenders.