The long-term efficacy and tolerability of azelastine (CAS 58581-89-8) nasal spray (0.14 mg/nostril b.i.d.) was investigated in patients suffering from perennial allergic rhinitis. 185 patients entered an initial 6 months' study; 35 of them continued in a follow-up for a further 30 to 60 weeks' treatment. Azelastine both attenuated the severity and reduced the incidence of rhinitis symptoms, with the highest rate of improvement during the first month with some additional improvement during the following months. The most marked effects were on those symptoms which were initially most severe: nasal obstruction, mucosal swelling, rhinorrhoea, sneezing and nasal itching. Signs of rhinitis identified by rhinoscopic examination improved in parallel to symptoms. 84.1% of patients reported 'good' or 'very good' efficacy as did 94.3% during the follow-up. Approximately 96% of patients rated the tolerability of treatment as 'very good' or 'good'. The incidence of adverse events of possibly causal relationship to azelastine treatment was low during the first 6 months. The most frequent events were the experience of application site reactions (e.g. burning) and bitter or unpleasant taste, specific to azelastine. No unwanted effects were reported by patients continuing treatment. In addition, results of nasal biopsies indicate that with the dose used azelastine nasal spray is a safe drug for long-term treatment of perennial allergic rhinitis.