The Perceived Stress Scale (PSS) is a widely used measure of stress that has not been validated in asthma patients. The psychometric properties of the PSS were explored using confirmatory factor analysis and item response theory. Study 1 involved 312 ambulatory care patients with asthma who completed the PSS during a routine visit. Study 2 involved 247 community-dwelling adults with asthma who completed the PSS as a part of a larger asthma study. Four items showed acceptable psychometric performance across ethnic groups and literacy. The short PSS is a rapid, valid measure of subjective stress in diverse asthma populations.