We investigated whether 12 weeks of rehabilitation at home in patients with chronic obstructive pulmonary disease (COPD) had a beneficial effect on lactate production, metabolic gas exchange data, workload of the inspiratory muscles, and dyspnoea during a maximal bicycle ergometer test. A second aim was to assess whether a change in dyspnoea was related to a change of inspiratory muscle workload. Forty three COPD patients with severe airways obstruction were included in the study: mean forced expiratory volume in one second (FEV1) 1.3 +/- 0.4 L (44% predicted), mean FEV1/inspiratory vital capacity (IVC) 37 +/- 8%. Twenty eight patients started a rehabilitation programme, whilst 15 patients received no rehabilitation. Rehabilitation was carried out at home; patients were supervised by a general practitioner, a physiotherapist and a nurse. Exercise tolerance was measured by means of a 6 min walking distance test (6MWD) and maximal workload (Wmax) during an incremental symptom-limited cycle ergometer test. Inspiratory muscle workload at Wmax was assessed with the Tension Time Index (TTI), and dyspnoea at Wmax with the Borg scale. After 12 weeks, the rehabilitation group showed a significantly larger increase in 6MWD (from 438 to 447 m) and in Wmax (from 70 to 78 W) compared with the control group. A significant improvement in oxygen consumption (V1O2) (from 1.0 to 1.1 L), lactate level (from 3.7 to 3.1 mEq.L(-1)), dyspnoea (from 6.0 to 4.5) and TTI (from 0.10 to 0.08) at Wmax occurred in the rehabilitation group during the programme. The reduction in TTI was not significantly correlated with the fall in dyspnoea, as assessed by the Borg scale. We conclude that 12 weeks of rehabilitation at home in COPD patients increases symptom-limited V1O2 in combination with an increased Wmax. At this significantly higher Wmax, there was a reduction in dyspnoea, lactate level and inspiratory muscle workload. The reduction in dyspnoea was not related to a decreased inspiratory muscle workload. This study shows that rehabilitation at home can produce beneficial physiological improvements during exercise in patients with chronic obstructive pulmonary disease.