Pulmonary function test results of individuals with the acquired immunodeficiency syndrome (AIDS) were analyzed to determine the prevalence of abnormally low forced expiratory flow rates and bronchial hyperreactivity. Of 99 individuals with AIDS, a total of 44 (44 percent) had either low forced expiratory flow rates or a significant response to inhaled bronchodilator. Thirty-one (31 percent) individuals exhibited significant improvement in airflow rates after bronchodilator inhalation, while 33 (33 percent) had low flow rates. Twenty (20 percent) individuals had both low flow rates and a significant response to bronchodilator. In 83 percent of symptomatic individuals treated with bronchodilators there was clinical improvement. Thus, we conclude that abnormally low forced expiratory flow rate with or without bronchial hyperreactivity is a common and treatable complication of AIDS.