Research clarifying the role of the parasympathetic nervous system in the pathophysiology of chronic obstructive pulmonary disease (COPD) has renewed interest in anticholinergic therapy of these disease processes. The investigational agent ipratropium bromide produces bronchodilation by competitive inhibition of cholinergic receptors on bronchial smooth muscle, antagonizing the action of acetylcholine. When administered via inhalation at therapeutic doses of 20-40 micrograms, ipratropium is somewhat less effective than beta-agonists in asthmatics. In the treatment of chronic bronchitis, however, ipratropium appears at least as effective as, and possibly superior to, the sympathomimetics. Combination therapy with beta-agonists or theophylline has resulted in enhanced effect over single-agent regimens. Due to the low serum concentrations achieved following inhalation, ipratropium has been well tolerated and is virtually free of significant adverse reactions. The primary role of ipratropium in therapy remains to be defined but appears to be as an alternative to beta-agonists in patients who fail to respond or who experience troublesome side effects. In addition, combination therapy may prove to be another important use of ipratropium in the management of COPD.