The aim of this study was to compare the effects of pharmacological reversal of neuromuscular blockade on static compliance and resistance in patients with and without chronic obstructive pulmonary disease (COPD). Twenty patients were studied: 12 patients were free of respiratory disease (NCOPD) and had normal pulmonary function tests. Eight subjects (COPD) had a clinical history of chronic bronchitis and a FEV1 < 70% of the predicted value. All patients were anaesthetised with a continuous infusion of methohexitone and alfentanil. Airway pressure (Paw) was recorded continuously. Static compliance (Crs) was calculated from the relationship between 21 syringe volume (250 ml step) and Paw. Total respiratory resistance (Rrs) was measured at two levels of inspiratory flow and tidal volume. These measurements were made before vecuronium (control), after injection of vecuronium to abolish the first neuromuscular response to train of four, 5 and 15 min after administration of neostigmine 40 micrograms.kg-1 and atropine 10 micrograms.kg-1. In COPD patients Crs and Rrs were significantly greater (1450 +/- 580 ml.kPa-1 and 1.06 +/- 0.68 kPa.l-1.s-1) than in normal patients (1000 +/- 380 ml.kPa-1 and 0.58 +/- 0.22 kPa.l-1.s-1) (P < 0.01). In both groups Crs and end-expiratory pulmonary volume were similar before injection of vecuronium and after neostigmine-atropine administration. In both groups, Rrs was not altered significantly by neostigmine-atropine for the two inspiratory flows. These results suggest that neostigmine-atropine mixture is associated with small changes in respiratory mechanics, and the changes are similar in COPD compared with normal patients.