The chemistry, pharmacology, pharmacokinetics, clinical efficacy, adverse effects, and dosage of ipratropium bromide are reviewed. Ipratropium bromide, a synthetic quaternary isopropyl derivative of atropine, interrupts vagally mediated bronchoconstriction by inhibiting the cyclic guanosine 3',5'-monophosphate system at parasympathetic nerve endings. Ipratropium bromide is poorly absorbed after oral and inhaled administration but diffuses rapidly into tissue after i.v. or i.m. administration. The elimination half-life is 3.2-3.8 hours. After inhalation, the drug is eliminated in the urine and feces. The bronchodilatory effect of ipratropium bromide in stable chronic obstructive pulmonary disease appears to be comparable, and may be superior, to that of the beta-sympathomimetic agents. In acute exacerbations, ipratropium bromide is useful but may not be the preferred agent because of a delayed onset of action (within 15 minutes; mean dose-dependent duration of effect, three to five hours). Combination therapy with other bronchodilating drugs has proved useful. Ipratropium bromide may be a useful adjunctive agent in the treatment of asthma. Since the onset of action is delayed, ipratropium bromide should not be used as single-drug therapy in an acute asthmatic exacerbation. Reported adverse effects, including cough, nausea, palpitations, dry mouth, nervousness, gastrointestinal distress, and dizziness, have been mild. The usual dosage is two inhalations (36 micrograms) four times daily, and the maximum number of doses per day should not exceed 12. Although ipratropium bromide is currently indicated only for maintenance therapy in stable chronic bronchitis and emphysema, it may be useful as adjunctive therapy in asthma and in the management of acute exacerbations of chronic bronchitis and asthma. Additional experience in a variety of chronic obstructive pulmonary disorders will help to clarify the role of ipratropium bromide in the treatment of obstructive pulmonary disease.