To the Editor.
—Vlahov et al1 recently found higher human immunodeficiency virus type 1 (HIV-1) seroprevalence among female than male inmates in nine of 10 US correctional facilities surveyed. Seroprevalence among younger women (<26 years) was higher than among younger men but similar to that in both older women and older men. In their blinded study, Vlahov et al were unable to evaluate the extent to which female inmates were more likely to be intravenous drug users and to have acquired HIV-1 infection through parenteral transmission.We reviewed the results of an anonymous 1987 survey of 3037 inmates in the Cook County (Illinois) Department of Corrections in order to determine if female inmates were more likely than male inmates to have a history of injectable drug use. In stratified analyses adjusted for differences in race-ethnicity and age, female inmates were almost twice as likely as male inmates to report