The efficacy and tolerability of azelastine (CAS 58581-89-8) nasal spray (0.14 mg/nostril b.i.d.) and budesonide (CAS 51333-22-3) nasal aerosol (0.05 mg/nostril b.i.d.) were compared in a 6-week, multicentre, parallel group study of 193 patients suffering from perennial allergic rhinitis. Total rhinitis symptoms complex (TSC) scores derived from 10 rhinitis symptoms improved during treatment by a mean of 11.4 +/- 6.8 with azelastine and 10.8 +/- 6.4 with budesonide. Response rates, defined as a decrease in TSC of at least 50% at the end of therapy, was 79% with azelastine and 73% with budesonide. There were no significant differences between the treatment groups with respect to either target variable. Objective measurements of nasal flow rate showed a return to normal values during the 6-week therapy. Signs of rhinitis identified by rhinoscopic examination improved in parallel to symptoms. Both medications were well tolerated. The incidence of adverse events of possibly causal relationship to therapy was low. The most frequent event in azelastine treated patients was the experience of an "unpleasant" taste or smell. Occasional epistaxis occurred in both treatment groups but more frequently with budesonide. Results indicate that with the dose used azelastine nasal spray is an effective treatment for perennial allergic rhinitis comparable to that of budesonide nasal aerosol.