Ipratropium bromide is an anticholinergc bronchodilator administered by inhalation. Although producing bronchodilation in most patients with obstructive airways disease, it is somewhat less effective than beta 2-adrenoceptor agonist drugs such as salbutamol or fenoterol in patients with asthma, but is at least as effective as these agents in bronchitis. As with the beta 2-adrenoceptor agonists, the onset of maximum effect with ipratropium (about 1.5 to 2 hours) is slower than with isoprenaline (although significant bronchodilation usually occurs within seconds or minutes of ipratropium inhalation), and the duration of effect (about 4 to 6 hours) is longer. Studies of concomitant use of ipratropium and other agents such as beta 2-adrenoceptor agonists, theophylline, or sodium cromoglycate, have usually shown a greater response in many patients than with single drug therapy, as might be expected from the different mechanisms of action of these groups of drugs. Usual inhaled doses of ipratropium were well tolerated in all studies. Ipratropium thus appears to be a suitable alternative to beta 2-adrenoceptor agonist drugs in patients not fully responding to these agents, and combined therapy with ipratropium and other bronchodilating drugs may prove to be an important area of use in patients failing to respond adequately to a single drug regimen. (nevertheless, in asthma patients in whom a 'non-responsive' state is developing, initiation of corticosteroid therapy should not be delayed). Ipratropium may also be useful in the occasional patient in whom side effects such as palpitations or tremor are troublesome with usual inhaled doses of beta 2-adrenoceptor agonists.