The findings show that most male IVDUs are sexually active and many have multiple female partners. Black male IVDUs are more likely to have relations with a non-IVDU female and are more likely to have more than one partner. Although a large number of female IVDUs have had multiple partners, many of them non-IVDUs, the modal response for both black and white female IVDUs is to have one male sex partner. Male IVDUs with either a single or multiple partners, and either IVDU or non-IVDU, reported having between one and five sexual encounters per week. The frequency of sexual contact among female IVDUs also appears stable, whether the respondents had one or more partners. Although the rate of condom use was small among all male IVDUs, the percent who use them occasionally is higher among males with multiple partners. Men are no more likely to use condoms with prostitutes than with non-prostitutes, and men who have multiple partners are more likely to engage in anal intercourse. Females are more likely to use condoms with a non-IVDU partner and with multiple partners. Furthermore, white women and women with multiple partners are more likely to engage in anal intercourse. These high risk behaviors pose a serious threat of HIV transmission to the non-IVDU population. 7 tables, 5 notes, 24 references. (Author abstract modified)