Mucous impaction may be suspected in asthmatic exacerbation when, despite aggressive medical management, patients continue to produce sputum containing mucous plugs and exhibit prominent rhonchi and/or wheezes on chest auscultation. Spirometric measurements in this setting corroborate lack of improvement and reveal significant impairment in indices that may reflect small airways function (FEF25-75). We hypothesized that clearance of inspissated secretions by fiberoptic bronchoscopy with lavage (FOBwL) may promote or hasten the clinical improvement of such patients. Fifty-one therapeutic FOBwL were accomplished in 19 patients during 20 episodes of stabilized yet refractory asthma with mucous impaction. No significant complications were encountered. After FOBwL, spirometric measurements of FEV1, FEF25-75, and FVC increased significantly (P less than. 01, paired t test), and correlated with relief of dyspnea and mobilization of secretions with cough. FOBwL can be safely performed in stabilized, refractory asthma, and with apparent efficacy. Further investigation is needed to document the therapeutic utility of FOBwL in refractory asthma.