In vivo exposure homework was applied to a consecutive series of 30 outpatients suffering from DSM-IIIR panic disorder with agoraphobia. Assessment of the characteristics of panic attacks (the prodromal phase immediately preceding the attack, acute peak anxiety, and the residual phase immediately afterwards) was done by an independent rater before treatment, after six sessions and at the end of therapy (12 sessions). Twenty-five of the 30 patients completed treatment. All of them still reported panic attacks after six sessions, even though the characteristics of panic partially improved. At the end of therapy, panic attacks disappeared in 21 of the 25 patients (84%) and these gains were maintained to 1 year follow-up thereafter by the majority (81%) of subjects.