Before the early 1870's, prisoners were not classified by sex or housed in separate facilities. The protection of women was the rationale for the creation of women's institutions. However, the policy of separation works to deprive both female and male inmates of a full range of facilities, services, and opportunities. Women's facilities often provide fewer services and impose more restrictions than do those for men. Segregation by sex perpetuates sexual stereotypes that degrade both sexes. Moreover, sexual segregation does not further the societal interests of punishment, deterrence, incapacitation, or rehabilitation. Maintaining single-sex prisons does not appear to be less expensive or easier than running mixed facilities. Correctional administrators justify and rely on sexual segregation as a principal technique for solving the problems of exploitation and victimization among inmates. However, separating women and men avoids only exploitation between the sexes. It does not prevent the many acts of victimization that occur in single-sex facilities. Sexual segregation thus produces an illusion of safety that diverts attention from this substantial problem. The problems which should be addressed are numerical ratios and victimization rather than the sexual identity of prisoners. Reference notes are provided.