Despite the increasing use of dry powder formulations in the ambulatory setting, there is a paucity of information on the efficacy of this therapeutic modality to treat acute severe asthma. In addition, studies that compared wet nebulization vs metered dose inhalers formulated with chlorofluorocarbon (CFCMDI) attached to holding chambers have yielded discrepant results. Thus, it is unclear which of the three delivery systems would elicit a superior bronchodilator response, particularly in patients with life-threatening asthma. In a prospective, randomized open design, we studied the response to inhaled albuterol (salbutamol) in 27 adult asthmatics presenting to the emergency department (ED) with an FEV1 <30% predicted. Subjects were treated with one of the following regimens (nine subjects in each group): group A, mean (SD) baseline FEV1 of 0.7 (0.2) L, received albuterol solution, 5 mg, via a nebulizer (Puritan-Bennett Raindrop; Lawrenceville, Ga) impelled with oxygen (O2) at 8 L/min; group B, baseline FEV1 of 0.6 (0.15) L, received albuterol, 400 microg, via a CFCMDI attached to a 145-mL valved aerosol holding chamber (Aerochamber; Trudell Medical; London, ON); and group C, baseline FEV1 of 0.6 (0.17) L, received albuterol powder, 400 microg, by another means (Rotahaler; Glaxo; Research Triangle Park, NC). All groups received the respective treatments on arrival in the ED, every 30 min during the first 2 h, and then hourly until the sixth hour. Clinical parameters and FEV1 were recorded on ED admission and 15 min after each dose of albuterol. At the time of ED admission, all patients also received continuous O2 and one dose of I.V. steroids (dexamethasone, 8 mg). The total dose of inhaled albuterol administered during the 6-h treatment was 45 mg of nebulized solution in group A and 3,600 microg of albuterol aerosol and dry powder in groups B and C, respectively. No significant differences were found in the population demographics, baseline FEV1, and arterial blood gas values on air. FEV1 improved significantly in all patients after the 6 h of treatment. The 6-h area under the curve FEV1 improved similarly with the three delivery methods despite differences in the total dose administered. No patient was discontinued during the trial or admitted to hospital and no evidence of cardiovascular adverse events was apparent in any of the study groups. These data support the view that the three delivery methods appear adequate to treat subjects with acute severe asthma.