Anticholinergics are commonly used in the treatment of airway diseases. While their effectiveness in chronic asthma offers no advantage over beta-agonists, evidence continues to accumulate suggesting substantial additional benefit in acute asthma attacks. This increased response to anticholinergics suggest that cholinergic bronchoconstriction is increased in acute asthma. Multiple mechanisms related to changes in expression and function of inhibitory M2 muscarinic receptors on the airway parasympathetic nerves may be involved, and are discussed. The use of anticholinergics in chronic obstructive pulmonary disease and in rhinitis are also considered.