The purpose of this study was to validate a vertical visual analogue scale (VVAS) as a measure of clinical dyspnea. Concurrent validity was demonstrated by having asthmatics score their dyspnea intensity on both a VVAS and a horizontal visual analogue scale (HVAS), and then measuring their peak expiratory flow rate (PEFR). Correlation between the VVAS and HVAS was r = .97; between the VVAS and the PEFR, correlation was r = -.85, demonstrating the concurrent validity of the VVAS as a measure of dyspnea. Construct validity then was established, using the contrasted-groups approach with repeated measures. Both asthmatics and those with chronic obstructive lung disease (COPD) rated their dyspnea on the VVAS during times of severe and little airway obstruction. The dyspnea ratings at times of severe versus low obstruction were found to be different for both the asthmatic and COPD subjects. The VVAS was shown to have both concurrent and construct validity as a measure of dyspnea.