OBJECTIVE: To determine the incidence of residual pneumothorax after video-assisted thoracic sympathectomy, with and without postoperative pleural drainage, and to evaluate the possible influence of this type of pneumothorax on postoperative pain within the first 28 postoperative days. METHODS: All patients presenting symptoms consistent with primary palmoplantar hyperhidrosis and treated at the Thoracic Surgery Outpatient Clinic of the State Hospital of Sumaré between July and December of 2006 were included. All were submitted to sympathectomy up to the third ganglion using video-assisted thoracoscopy and were randomized to receive or not receive postoperative pleural drainage for 3 h. Chest X-rays and low-dose computed tomography scans of the chest were performed on the first postoperative day in order to determine the incidence of residual pneumothorax. At different time points up to postoperative day 28, patient pain was assessed using a visual numeric scale and by measuring the quantity of opioid analgesics required. RESULTS: This study comprised 56 patients, 27 submitted to bilateral pleural drainage and 29 not submitted to drainage. There was no statistical difference between the two groups in terms of the incidence of post-sympathectomy residual pneumothorax. Residual pneumothorax diagnosed through any of the methods did not influence pain within the first 28 postoperative days. CONCLUSION: Performing closed pleural drainage for 3 h immediately after video-assisted thoracic sympathectomy did not affect lung re-expansion or the incidence of residual pneumothorax. When residual pneumothorax was present, it did not affect pain within the first 28 postoperative days.