A simple spirometer was tested in an outpatient family practice to determine whether its use increased detection of chronic obstructive airway disease (COAD) in patients at risk, more accurately identified patients with reversible bronchospasm, and helped to make the most of their bronchodilator therapy. Three (17 percent) of 18 patients at risk, previously unlabeled, were found to have COAD. Of 28 patients with a previous COAD diagnosis, 5 (18 percent) had the diagnosis deleted, and 5 who had previously been classified as "reversible" were reclassified as having "irreversible" bronchospasm (P less than .025). Of 46 patients studied, bronchodilator therapy was changed in 18 (39 percent); 12 of these improved symptomatically according to a subjective score (P less than .02). A few patients demonstrated a significant improvement in 1-second forced expiratory volume.