Clinicians and surgeons have used the subjective response to the climb of "one or two flights of stairs" to assess the "reserve" of patients with chronic airflow obstruction (CAO). Very little objective data exist regarding the metabolic and ventilatory cost for any level of stair climbing in these patients. Therefore, this study was designed to evaluate the use of symptom-limited stair climbing as a simple method to estimate the peak oxygen uptake (VO2) and minute ventilation (VE) in patients with CAO. We studied 31 men with varying degrees of CAO, who climbed stairs until they stopped at their symptom-limited maximum. During this climb, timed expired gas was intermittently collected and analyzed, and oxygen saturation and heart and respiratory rates were recorded. The patients achieved 81 +/- 14 percent of their predicted maximal heart rate and 90 +/- 27 percent of their predicted maximal VE. The number of steps or flights climbed correlated linearly with peak VO2 (r = 0.72, p < 0.01) and with VE (r = 0.7, p < 0.01). Stair climbing peak VE, VO2, heart and respiratory rate correlated well with those achieved during standard leg cycle ergometry. The mean +/- SD number of flights climbed was 4.2 +/- 1.7 with most patients (87%) reaching at least 3 flights (54 steps). The group of eight patients with very severe CAO (FEV1 < 0.9 L) climbed 3.4 +/- 0.9 flights (61 +/- 16 steps). We conclude that a symptom-limited maximal stair climb helps estimate peak VO2 and VE in patients with CAO. The frequently advocated test to climb one to two flights to evaluate cardiopulmonary reserve is not adequate for most patients with CAO. Symptom-limited maximal stair climbing is a simple, inexpensive and readily available test that may be used to evaluate the cardiopulmonary reserve of stable patients with CAO.