The present study is concerned with plasma beta-endorphin and glucose tolerance in patients with chronic obstructive pulmonary disease (COPD). Plasma beta-endorphin, glucagon and insulin concentrations were measured during an oral glucose tolerance test in 20 COPD patients and in 18 age-matched healthy controls (mean age 62 years). Seven patients had a moderate COPD (group I) and seven a severe COPD (group II). The remaining six severe COPD patients received long-term oxygen therapy (group III). We found that fasting levels of beta-endorphin were significantly increased in all patient groups compared to healthy controls (p < 0.01, 0.05 and 0.005, respectively). Six of the 13 severely diseased COPD patients had impaired glucose tolerance. Plasma beta-endorphin levels decreased significantly during OGTT in the COPD patients (p < 0.05). Fasting beta-endorphin levels were higher in patients with impaired glucose tolerance than in those patients with normal OGTT (42.0 pmol/L +/- 11.4 SD versus 34.8 +/- 10.2). However, this difference was not statistically significant. In conclusion, this study showed that beta-endorphin concentrations are increased in COPD patients whether or not they receive oxygen therapy.