Objective: To assess the complications in a group of patients with palmar hyperhidrosis treated with transthoracic endoscopic sympathectomy. The extraordinarily high incidence of postoperative compensatory hyperhidrosis in our series is stressed and explained., Methods: The retrospective study included chart reviews and outpatient assessments. Seventy-two patients underwent T2 or T2-T3 endoscopic sympathectomy for primary palmar hyperhidrosis. Patients' hyperhidrosis severity, precipitating factors, postoperative complications, surgical results, and satisfaction were assessed. Severity of palmar hyperhidrosis and compensatory hyperhidrosis was classified by two grading scales., Results: The success rate of sympathectomy was 93%. All patients except one suffered from compensatory sweating, which was the main cause of patients' dissatisfaction postoperatively. Seventeen percent of the patients (12 of 72 patients) experienced new symptoms of gustatory sweating (facial sweating associated with eating). Twenty-one patients experienced other complications, including pneumothorax, Horner's syndrome, nasal obstruction, and intercostal neuralgia., Conclusion: Transthoracic endoscopic sympathectomy is an effective and simple modality to treat palmar hyperhidrosis. However, all patients need to be warned of the common complications, particularly compensatory hyperhidrosis, before surgery.