This study tested the utility of the theory of planned behavior (TPB) for understanding and predicting condom use intentions among male and female injecting drug users (IDUs). Interviews were conducted with 405 male and 315 female sexually active IDUs. Participants indicated their intentions to use condoms with main and nonmain sexual partners as well as attitudes, social norms, partner norms, and perceived behavioral control relevant to condom use with each partner type. The TPB accounted for 36 to 48% of the variance in intentions to use condoms. Intentions were related to attitudes, regardless of partner type. Partner norms were related to intentions to use condoms with main partners (men and women) and nonmain partners (men only). Social norms did not predict intentions, regardless of partner type. Perceived behavioral control was related to intentions to use condoms with main partners (men and women) and nonmain partners (women only). The findings are interpreted in light of the roles of cooperation, intimacy, and concern about self-protection.