Budesonide by inhalation and placebo were tested in 18 patients with moderate chronic bronchial asthma. Three dose levels of budesonide were used (25, 100 and 400 micrograms q.i.d.) and the patients were to take two puffs q.i.d. in all periods. The active treatment was investigated using double-blind cross-over technique, and placebo at the end of the trial. The duration of each treatment period was 2 weeks. The study showed a high drop-out frequency while on placebo and that the PEF values were influenced in a dose-dependent way by budesonide. In spite of the double-blindness the patients had a tendency towards overuse of the trial aerosol on the lowest dose, but they used significantly less than prescribed during the period with the highest dose. No side effects were reported.