The aim of this study was to evaluate the frequency and characteristics of peripheral nervous system involvement in chronic obstructive pulmonary disease and its relation with proinflammatory cytokines such as TNF-alpha, IL-6, IGF-1 and CRP. Forty chronic obstructive pulmonary disease patients with a mean age 62.8 +/- 5.5 years and 33 healthy controls with a mean age of 61.8 +/- 7.4 were included into this study. All subjects were evaluated with standard motor and sensory nerve conduction studies. Serum TNF-alpha, IL-6, CRP and IGF-1 were measured. The muscle strengths of three muscle groups (knee extensors, shoulder abductors and flexors) were assessed with a hand-held dynamometer. Peripheral neuropathy was detected at 15% of chronic obstructive pulmonary disease patients. Ulnar motor and sensory nerves, left sural nerve distal latencies were found significantly prolonged than healthy volunteers (p = 0.011), peroneal nerve conduction velocities was found lower in patients than in healthy controls (p = 0.021), tibial nerve amplitudes was found lower in patients than healthy controls (p = 0.046). CRP and TNF-alpha were found significantly higher in chronic obstructive pulmonary disease patients and IGF-1 was found significantly lower in chronic obstructive pulmonary disease patients. There was no correlations between proinflammatory cytokines, CRP and electrophysiological findings. Left sural nerve's sensory nerve action potential amplitude was correlated positively with FEV(1)% (r = 0.425; p = 0.009). Muscle strength at the shoulder and knee were significantly reduced in patients with COPD when compared with controls. The frequency of neuropathy was higher in chronic obstructive pulmonary disease when compared with the healthy controls. Chronic obstructive pulmonary disease patients have subclinical peripheral nerve involvements.