Thirty patients with seasonal allergic rhinitis entered a double blind study comparing budesonide (nasal spray, 400 micrograms/d) and i.m. injection of 80 mg methylprednisolone acetate. Symptoms were assessed over a "run in" period of 3-7 days followed by a treatment period of 3 weeks. Pollen counts were evaluated daily. Both the systemic and topical corticosteroid treatment resulted in a significant improvement of nasal and ocular symptoms and were accompanied by reduced antihistamine intake. A comparison of the two treatments in relation to the pollen count yielded statistically significantly fewer nasal symptoms, such as itching, secretion, and sneezing in the budesonide-treated group. Nasal blockage and ocular symptoms remained unchanged, but the use of eyedrops was significantly reduced in the methylprednisolone-treated group. Side effects of both treatments were mild and the incidence negligible. Methylprednisolone-treated patients had a significantly lower cortisol value after 7 days but still had a normal response to ACTH-stimulation. We conclude that the acute symptoms of allergic rhinitis are at least as well ameliorated by regular topical application of budesonide as by a single injection of methylprednisolone acetate. The accompanying allergic conjunctivitis may require additional treatment.