['Asymmetric dimethylarginine (ADMA) and nitric oxide (NO) show their mechanism of action reciprocally, the balance between these molecules contributes to the tight regulation of airways tone and function.', 'The aim of this study to determine the serum levels of ADMA and NO in patients with chronic obstructive pulmonary disease (COPD) and establish whether their level vary in relation to forced expiratory volume in 1s (FEV', 'This study consisted of 58 patients with COPD and 30 healthy subjects. Serum ADMA and NO levels were measured using enzyme-linked immunosorbent assay and the colorimetric method, respectively.', 'Serum ADMA levels were significantly higher, however, NO levels were lower in patients with COPD compared with controls. ADMA levels were inversely correlated with NO levels. Serum ADMA and NO were significantly correlated with FEV'] Does asymmetric dimethylarginine contribute to airway nitric oxide deficiency in patients with COPD?