This study examined the effects of a group focused on prevention of acquired immune deficiency syndrome (AIDS) on the knowledge, attitudes, and behavioral intentions of participants. Persons in treatment for substance abuse participated in either one or two structured group experiences and completed an evaluation form that included measures of knowledge about HIV infection and AIDS prevention. Additionial measures of perceived relevance, behavioral intenitions, and attitudes toward condom use were also included. Results indicated that whereas participants in the groups demonstrated significantly higher levels of knowledge regarding HIV inzfection and prevention, their attitudes concerning behavior change and perceived relevance were not significantly different from clients in a wait-list control group. Post hoc analyses revealed that participants 'biases against condom use predicted behavioral intentions to take precautionary measures. Implications regarding cognitive processing models of persuasioni in therapy and prevention programs are discussed.