Compensatory hyperhidrosis is a common and potentially severe side effect of bilateral endoscopic thoracic sympathectomy. We describe a patient with severe compensatory hyperhidrosis as a result of this procedure. We treated the patient with 2 separate series of subcutaneous botulinum toxin type A injections to the right upper abdomen and achieved anhidrosis in 5 weeks. Although botulinum toxin is already an established treatment modality for primary hyperhidrosis, there is little experience using it for the treatment of compensatory hyperhidrosis. Because of its efficacy and low side-effect profile, we believe botulinum toxin may play a significant role in treating compensatory hyperhidrosis as a first-line agent.