The anticholinergic, antimuscarinic compounds are potent and hitherto neglected bronchodilators. Although atropine itself has drawbacks, principally related to its rapid absorption and consequent systemic side effects, its quaternary ammonium congeners, atropine methonitrate and ipratropium bromide, are poorly absorbed. When given by inhalation, they are as effective bronchodilators as atropine is, but longer acting and much less prone to side effects. They act predominantly at a site that is different from adrenergic agents and thus afford an alternative, complementary approach to the treatment of airways obstruction. In stable asthmatic subjects, ipratropium is almost as potent a bronchodilator as β2-adrenergic agents are. In patients with chronic bronchitis and emphysema, it is more potent than β2-adrenergic agents are. In both conditions, its combination with other bronchodilators adds significantly to the level and duration of bronchodilatation. It may also be occasionally useful in counteracting bro...