The new dry-powder inhaler system, Turbuhaler®, has proved to be equivalent to metered-dose inhalers when used in the nose, and the objective of this study was to investigate the efficacy, dose-response effects, and safety of budesonide powder given in the morning during the grass pollen season to patients with grass-pollen-induced allergic rhinitis. Of 190 randomized patients, 186 were treated and 180 completed this double-blind study, which comprised a 4-week treatment period, preceded by a 1-week run-in period. The patients were randomized to three parallel treatment groups: budesonide 400 μg, budesonide 200 μg, or placebo once in the morning. Assessment of efficacy, by comparing changes in mean scores of nasal symptoms from run-in to treatment, showed a statistically significant effect for all symptoms with active treatments, as compared with placebo. The mean reduction of symptom severity was more pronounced in the 400-μg group than in the 200-μg group, and this difference was statistically significant for runny nose (P<0.02) and combined nasal symptoms (P<0.02). Nasal peak-inspiratory flow improved significantly in both budesonide-treated groups, as compared with placebo (P<0.01 and P<0.01). During the treatment period, patients on active treatment showed, on average, a reduction of all nasal symptoms, whereas the placebo-treated patients, on average, showed an increase of nasal symptoms. Approximately 40% in the high-dose group felt total control of rhinitis symptoms, as compared with 26% in the low-dose group. There was no difference between budesonide- and placebo-treated groups in side-effects. Budesonide delivered from a Turbuhaler once daily in the morning is effective, and better symptom control is achieved by 400 μg than 200 μg in the treatment of seasonal allergic rhinitis. However, the low dose may be sufficient in patients with mild symptoms. Budesonide from a Turbuhaler may be preferable to pressurized-dose aerosols and aqueous pump sprays because it does not contain carrier gas, preservatives, or lubricants.