Many studies have focused on the systemic effects of chronic obstructive pulmonary disease (COPD), but none has examined neuromuscular junction transmission (NMT). We evaluated NMT dysfunction using single-fiber electromyography (SFEMG) in patients with COPD. Twenty patients with COPD and 20 age-matched healthy controls were included in the study. All patients and controls underwent SFEMG. Abnormal NMT was found in seven of 20 patients (35%), but in none of the control subjects. The COPD patients were subgrouped according to the presence of hypoxemia. The patients with normoxemia were classified as Group 1, and the patients with hypoxemia were classified as Group 2. Abnormal NMT was found in six patients in Group 2 and in one in Group 1. While there was significant difference in terms of abnormal NMT between Group 2 and the controls, there was none between Group 1 and the controls. Our results show that NMT abnormalities can be present in hypoxemic patients with COPD. (C) 2013 Elsevier B.V. All rights reserved.