We have adapted a visual analogue scale (VAS) to make repeated measurements of the sensation of dyspnoea during an exercise test on a bicycle ergometer. We tested the reproducibility of the development of the VAS as a function of work load and its sensitivity in detecting changes in the sensation of dyspnoea induced by the addition of an inspiratory resistance or by a trial of oxygen administration in 13 patients who were dyspnoeic on effort. The reproducibility was acceptable providing to perform a preliminary test and to eliminate the rare subjects who was incapable of performing the test (1/13). The method turned out to be equally sensitive as to the effect of inspiratory resistance for 8/12 patients and for the oxygen enrichment of inspired air for 8/9 patients. This scale thus provides a reproducible and sensitive estimation of the sensation of dyspnoea during effort and thus appears valuable in evaluating the subjective response in therapeutic trials in patients who are dyspnoeic on effort.