Bronchodilator therapy is lifelong mandatory for chronic obstructive pulmonary disease patients. There is evidence of loss of bronchodilator effectiveness over time with beta2-agonists but not with anticholinergics. The aim of this study was to examine the development of tachyphylaxis to the long-acting beta2-agonist salmeterol using as a control therapeutic regimen the combination of ipratropium bromide and salbutamol sulphate. Fifty-six subjects participated in a 20-week, crossover randomised clinical trial. The parameters forced expiratory volume at 1 s (FEV1), peak expiratory flow rate (PEFR) and FEV1/forced vital capacity were measured via spirometry and the parameters triangle DeltaFEV1%pre, triangle DeltaPEFR%pre and triangle DeltaAUC(0-2 h) were calculated. FEV1 increased significantly after two weeks of treatment with the combination treatment but not with the salmeterol. The observed diminished increase could be attributed to the development of tolerance to the long acting beta2-agonist. Salmeterol seems to be an effective bronchodilator, however, its duration of action over time and its peak effect might be subject to tachyphylaxis.