SummaryIn a double blind, randomized study, the effects of powder inhalation of 40figversus 400figof ipratropium bromide were compared in ten patients with obstructive lung disease in whom 2 X 20figof the commercial dose-aerosol (Atrovent®) was ineffective (mean change in FEV, after 15 min: + 4, 7 %).Both doses of powder inhalation caused a clearcut bronchodilation which generally reached a plateau between 30 and 180 min. 400figwas slightly more effective than 40figalthough the differences were statistically significant only at some time points: after 30 min the change in FEV, was 26±13 (SD) % versus 16±11 % (p<0.05).There were no appreciable side effects even not with the high dose.