In a multicenter placebo-controlled study, the safety, side effects, and patient acceptance of alprazolam for the treatment of panic disorder and agoraphobia were examined. A total of 525 patients meeting DSM-III criteria for agoraphobia with panic attacks or panic disorder were randomly assigned to receive alprazolam or placebo, which they took for eight weeks. The mean daily dose at the end of the study was 5.7 mg of alprazolam or 7.5 capsules of placebo daily. Potentially serious reactions to alprazolam occurred in ten of 263 subjects who received the drug. These included acute intoxication (three), hepatitis (two), mania (two), amnesia (one), aggressive behavior (one), and depression (one). Treatment-related side effects that were worse in patients taking alprazolam than in those taking placebo included sedation, fatigue, ataxia, slurred speech, and amnesia. Sedation was the most frequent but tended to subside with dose reduction or continued administration of the drug. Patient acceptance of alprazolam, as measured by the rate of completion for study participants, was high. Eighty-four percent of patients receiving active drug completed the study compared with 50% receiving placebo.