Following promising preliminary evidence, the benzodiazepine-derivative alprazolam was studied in a large, placebo-controlled, eight-week, flexible-dose trial in patients with agoraphobia with panic attacks and panic disorder. Of 526 patients, 481 completed three weeks of treatment; however, significantly more placebo (102/234) than alprazolam (21/247) recipients subsequently dropped out of the trial, primarily citing ineffectiveness (of placebo) as the reason. Alprazolam was found to be effective and well tolerated. There were significant alprazolam-placebo differences in improvement for (1) spontaneous and situational panic attacks, (2) phobic fears, (3) avoidance behavior, (4) anxiety, and (5) secondary disability, all significant by the end of week 1. At the primary comparison point (week 4), 82% of the patients receiving alprazolam were rated moderately improved or better vs 43% of the placebo group. At that point, 50% of the alprazolam recipients vs 28% of placebo recipients were free of panic attacks.