Oxitropium bromide (OB) is a quaternary ammonium congener of hyoscine with anticholinergic properties. We studied its bronchodilating properties in 14 patients with chronic obstructive lung disease without features of asthma in whom theophylline and other bronchodilators were withheld. Five doses of OB(20, 40, 100, 200, and 400 micrograms) as well as 150 micrograms of isoproterenol (ISO) and placebo were administered by metered-dose inhaler on separate occasions in a double-blind fashion. Pulmonary function (flow volume loops and airways resistance), blood pressure, and pulse rate were measured at baseline and periodically for eight hours after drug administration. Onset of bronchodilator effect was within five minutes for OB (P less than .025). Duration of action of OB was at least eight hours (P less than .025). The dose response characteristics of OB were examined by correlating the log dose with the areas under the time-FEV1 curve (r = .97, P less than .01), the time-forced vital capacity curve (r = .98, P less than .01), and the time-SGAW curve (r = .83, P less than 0.1). For FEV1, doses of 40 to 400 micrograms were significantly better than placebo and 100 to 400 micrograms were better than ISO (P less than .01). For forced vital capacity, all doses of OB were better than placebo (P less than .05). For SGAW, the response to the 100- and 400-micrograms doses were significantly better than placebo and isoproterenol (P less than .05). There were no significant effects of OB on pulse, blood pressure, or electrocardiogram. No side effects were noted from the use of OB.(ABSTRACT TRUNCATED AT 250 WORDS)