The frequent occurrence of bronchospasm due to aerosolized pentamidine (AP) may reduce delivery of drugs to distal airways and produce symptoms that limit therapy. This study performed spirometric measurements before and after AP treatment in 30 human immunodeficiency virus seropositive patients over 18 months. Patients reporting symptoms of bronchospasm were treated with prophylactic beta-agonist aerosol before subsequent AP treatment. Forty percent of patients reported symptoms. This group had significant declines in forced expiratory volume in 1 second associated with AP, whereas the asymptomatic group had no decline in forced expiratory volume in 1 second. Bronchodilator prophylaxis eliminated AP-induced symptoms and spirometric changes. Baseline spirometry did not change after five monthly treatments. The close relationship between symptoms and acute spirometric changes, the lack of progressive airway obstruction due to AP, and the reliable response to beta-agonist therapy make a symptom-based approach to treatment possible.