R.J. is a 14-year-old female who was referred for severe separation anxiety, school phobia, and the recent onset of panic attacks. Despite 6 months of aggressive behavioral modification, she continued to be severely impaired by her symptoms. Pharmacotherapy with a benzodiazepine was initiated, immediately after receiving her initial dose of 0.5 mg of clonazepam, R.J. started laughing inappropriately and was giddy, agitated, and anxious. These symptoms spontaneously abated 4 hours later, Follow-up history indicated no previous reaction in R.J. or any family member. Treatment with chlordiazepoxide was helpful in reducing her anxiety symptoms without untoward adverse effects.