Thirteen children with perennial bronchial asthma, with a mean age of 11.2 years, were studied concerning the bronchodilatory effect of ipratropium bromide in cumulative doses. All the children had reduced basal forced expiratory flow (FEV1) and bronchial reversibility of at least 20% after inhalation of salbutamol. The study had a double-blind design with a crossover technique. The inhaled dose of ipratropium bromide solution was increased stepwise from 25 micrograms to 500 micrograms and saline was used as the placebo. FEV1 was recorded 20, 40, and 60 minutes after inhalation of the test solution. At the lower ipratropium bromide dose levels no bronchodilatory effect was seen, but 60 minutes after the inhalation of 500 micrograms ipratropium bromide the increase in the FEV1 was significantly greater than that after placebo. Additional inhalation of salbutamol caused no further rise in FEV1. At the 500-micrograms level a fall in the heart rate was noted. No side effects occurred. We concluded that ipratropium bromide has bronchodilatory properties in childhood asthma when given in sufficiently high doses.