Abstract Background Endoscopic thoracic sympathectomy (ETS) has come into widespread use for palmar hyperhidrosis and other complaints of the upper limb and of the head and neck, but there are concerns about its safety. This review highlights the operative complications and long-term side-effects that may occur. Methods A Medline search was carried out using the terms ‘thoracoscopic sympathectomy’, ‘endoscopic thoracic sympathectomy’ and ‘complications’. References from identified articles were handsearched for further relevant articles. The senior author's experience and personal communications were also taken into account. Results and conclusion No death following ETS has ever been reported in the literature, but nine anecdotal fatalities are known, five resulting from major intrathoracic bleeding and three from anaesthetic mishap. Significant intrathoracic bleeding may occur in up to 5 per cent of patients but only a minority require thoracotomy; pneumothorax occurs in 2 per cent of patients and two instances of brain damage are known. In the longer term compensatory hyperhidrosis is extremely common and 1–2 per cent of patients regret having had surgery because of its severity. Horner's syndrome, on the other hand, is rare. Improvements in instrumentation, adequate training and careful patient selection may help reduce the drawbacks of ETS.