This chapter explores whether chemical castration can be justified as a form of criminal punishment. The author argues that castration via the drug medroxyprogesterone acetate (MPA), or some similar drug, does not achieve the punishment aims of retribution, deterrence, or incapacitation, but might serve as punishment in the form of rehabilitative treatment. However, current U.S. chemical castration statutes are too broad to be justified as rehabilitative. The state is warranted in targeting psychological states in criminal defendants for rehabilitative treatment where such states (a) act as a primary cause of a criminal offender’s crime and (b) give rise to extraordinary worries that the offender will recidivate. Current statutes qualify criminal offenders for castration who do not have overwhelming sexual urges or other psychological states causally related to their crime that may be treated with MPA. Thus, even assuming the efficacy of MPA, such statutes are unjustifiable because they apply chemical castration to offenders for whom castration will have no rehabilitative effect