Few studies have examined sexual risk behaviors among drug users in the context of their primary sexual relationships. The aim of this study is to examine characteristics of sexual partners associated with inconsistent condom use among a sample of 703 cocaine and opiate users from Baltimore, MD who participated in a network oriented intervention study of human immunodeficiency syndrome (HIV) risk behaviors among drug users. The current study examines relationship characteristics between drug users and their sexual partners (n=1003). Some of the study participants had more than one sexual partner, accounting for the greater number of sexual pairs than study participants. Study participants reported using multiple drugs (56% injected, 48% sniffed heroin, and 48% smoked crack) and that 70% of their sexual partners also used heroin and/or cocaine. Forty percent reported consistent condom use in the past 3 months. In multiple logistic regression, characteristics associated with consistent condom use were, the drug user being HIV infected; not living with their sexual partners; and not being financially interdependent. Previous research has demonstrated lower rates of condom use with main compared with casual and exchange partners. Primary sexual partners provide a sense of stability and introducing condoms may not be desirable or realistic. HIV prevention programs that target drug users should focus on the benefits, such as trust and a sense of security, and risks of not using condoms in primary relationships. Programs should also focus on enhancing communication and negotiation skills through targeting individuals as well as couples. (Author' s abstract)