High rates of unprotected sexual behaviors and the exchange of sex for crack have been reported among female crack cocaine users. This subpopulation of drug users is at significant risk for contracting and transmitting HIV and AIDS. To date, there has been no research comparing crack- and opioid-abusing women, particularly regarding their involvement in high-risk behaviors and other key background indicators for different subgroups of drug-abusing women. Sixty-one crack-abusing African-American women who recently entered an intensive outpatient treatment program were compared to 64 matched women whose primary drug of abuse was heroin. The opioid subgroup represented both those who were involved in methadone maintenance and those who were out of treatment. Higher rates of high-risk sexual behaviors were reported by the crack subgroup, including prostitution, number of sexual partners, and infrequency of condom use. As expected, i.v. drug use and high-risk behaviors associated with needle use were much higher among the opioid subgroup. Other significant differences were found between the two groups across key indicators. Individuals in the crack subgroup were younger, cared for more children, were less employable, were less likely to be married, and had more extensive lifetime substance abuse. Quantitative and qualitative background and clinical data are also presented. The nature of crack versus heroin abuse is also discussed, particularly in relation to high-risk sexual behaviors. Finally, the impact of the findings on developing appropriate treatment interventions for both groups is addressed.