This investigation employed a multiple baseline design across five participants to examine written emotional expression as an intervention to improve lung function in high school-aged students, college students, and adults with asthma. The predicted forced expiratory volume in 1 second (FEV[subscript 1] measure of large airway functioning) and forced expiratory flow (FEF[subscript 25-75] measure of small airway functioning) were evaluated using spirometry. In addition, anxiety was measured using state and trait anxiety self-report scales. Generally, results were effective. Individuals with asthma are at higher risk for increased hospitalization and death. For the school-aged population, asthma is associated with increased absenteeism, restriction of various class activities such as physical education, and poor relationships with peers. Therefore, adults and children with asthma are in need of services and school psychologists appear uniquely qualified to intervene. More recently, the role of the school psychologist is diversifying with corresponding training (e.g., wellness, consultation, prevention, assessment and treatment of health issues) in the areas of health-related disorders that involve a psychological component. (Contains 3 figures and 2 tables.)