This study investigated 2 methods of disseminating a cognitive-behavioral intervention for panic disorder (PD). Thirty-six Ss who met diagnostic criteria for PD according to the Anxiety Disorders Interview Schedule-Revised were randomly assigned to 1 of 3 conditions: bibliotherapy (BT), group therapy (GT), or a waiting-list control (WL) condition. Interventions lasted 8 weeks and were followed by a posttest, along with 3- and 6-month follow-up assessments. Results indicated that both the BT and GT treatments were more effective than the WL condition in reducing frequency of panic attacks, severity of physical panic symptoms, catastrophic cognitions, agoraphobic avoidance, and depression and that the BT and GT treatments were more effective in increasing self-efficacy. Both interventions maintained their effects throughout the follow-up periods and produced clinically significant levels of change among the majority of treated Ss.