The study was performed to assess the efficacy of three ipratropium/fenoterol combinations and salbutamol when administered as nebulizer solution to patients with reversible airway obstruction. 11 patients, of whom 10 completed, aged 18 years or over, were chosen. For inclusion they were required to demonstrate a 15% improvement in absolute FEV1 within 10 min of administering an inhaled beta-adrenergic agonist. The study consisted of a randomised, double-blind, cross-over comparison between three combinations of ipratropium/fenoterol and salbutamol: ipratropium 0.5 mg/fenoterol 1.25 mg; iptratropium 0.5 mg/fenoterol 2.5 mg; ipratropium 0.5 mg/fenoterol 5.0 mg, and salbutamol 5.0 mg. In this relatively small number of patients there was no overall significant difference between the three doses of combination when PEFR, FEV1 and FVC were considered. However, the results for each of the three combinations were better than those for salbutamol and these reached the level of statistical significance (p less than 0.01) for the medium and high doses. PEFR measured between 3 and 8 h again demonstrated improved results for the three combinations compared with salbutamol reaching a level of statistical significance (p less than 0.01) for the high and medium doses.