The efficacy and safety of the nasally administered histamine H1 receptor blocking drug Azelastine was investigated in an open, multicenter, randomized comparative trial with Ebastine in seasonal allergic rhinitis. 110 patients in two parallel groups were treated for 14 days and efficacy was assessed by the physician using a rating scale measuring 10 nasal and ocular symptoms of seasonal rhinitis (0 = absent, 1 = mild, 2 = moderate, 3 = severe). Tolerability was measured on the basis of reported adverse events. Both treatment groups had dramatic reductions in the physician's total symptom score following treatment (p < 0.0005). There was no significant difference between the two groups. Changes in individual rhinitis symptoms showed no differences between the two groups. During treatment, 19 patients had at least one adverse event, 13 in Azelastine group and 6 in Ebastine group; all were mild. The most frequent adverse events reported were somnolence (4 cases in Ebastine group) and a bitter taste (4 patients in the Azelastine group). In conclusion, the results of the study on 110 patients suggest that both Azelastine and Ebastine are effective treatments of the symptoms of seasonal allergic rhinitis. Both drugs were well tolerated.