Equine obstructive pulmonary disease, also known as heaves or recurrent airway obstruction (RAO) is a common equine pulmonary disease with some similarities to human asthma and COPD, which represents a major cause of morbidity and loss of lung performance. Salbutamol has been widely used for the treatment of human airway diseases and has usually been prepared as the racemic form of the drug. However, recently the R-enantiomer of salbutamol has been introduced into clinical practice in the treatment of asthma in humans and this has been suggested to be an improvement on the racemic form of the drug; therefore thus the S-enantiomer has been demonstrated to have adverse effects in the lung and thus using the R-enantiomer may improve the therapeutic ratio. However, little is known about the properties of the R- and S-enantiomers of salbutamol in equine airways and the present study has evaluated the relaxant effects of racemic β2-agonists in comparison with the R- and S-enantiomers in isolated equine isolated bronchi, as well as the bronchoprotective effects of these drugs on cholinergic and histaminergic pathway.