The respiratory inductance plethysmograph (RIP) was used to record resting breathing for 45 min in 12 patients with stable chronic obstructive pulmonary disease (COPD) and 8 age- and sex-matched control subjects. The COPD group had mean FEV1.0 of 31% predicted (range: 15 to 49%), mean PaO2 of 70 mmHg (56 to 83 mmHg), and mean PaCO2 of 37 mmHg (31 to 47 mmHg). All subjects were studied in the sitting position, and the rib cage (RC) and abdomen (ABD) RIP signals were simultaneously recorded on a polygraph and sampled at 20 Hz by a microcomputer. The summed RC and ABD signals were processed to create a spirogram from which the timing components of the respiratory cycle were subsequently analyzed. The mean number of breaths analyzed per subject was 702 +/- 213 (SD). Mean tidal volumes were identical in both groups. Inspiratory and expiratory times were significantly less (p less than 0.01), and mean inspiratory flow was significantly greater (p less than 0.01) in the COPD group. Frequency and minute ventilation also were significantly greater in the COPD group (p less than 0.005). Variability of breathing pattern, assessed in terms of coefficients of variation, was significantly less for TI, TI/Ttot, and VI in COPD patients than in normal subjects, even after sighs had been excluded from the analysis. We suggest that alterations in breathing pattern and its variability reflect changes in neural control of breathing consequent to disease.