This international, multicentre, randomized, double-blind, double-dummy, parallel-group trial was undertaken to compare the efficacy and tolerability of once-daily astemizole-D (10mg astemizole plus 240 mg pseudoephedrine) with beclomethasone nasal spray (0.05mg/ml) two puffs/nostril administered twice daily in a total of 204 patients with seasonal allergic rhinitis. Treatment duration was 4 weeks, Although investigator assessments of symptom severity were generally comparable in the two treatment groups throughout the trial, statistically significant differences in favour of astemizole-D for sneezing and ocular symptoms were apparent at the end of the 4-week treatment period (P < 0.05). Patient diary data support these findings, with significant differences in favour of the antihistamine/decongestant combination reported for ocular symptoms after 2 weeks of treatment (P < 0.05) and non-significant trends for sneezing after 2 weeks and ocular symptoms over the entire treatment period (P= 0.07). Use of rescue medication for ocular symptoms was also significantly lower in the astemizole-D treatment group (P < 0.05). A wide range of adverse experiences were reported, however, there were no statistically significant differences in the type or incidence of those between the two treatment groups. In conclusion, astemizole-D appears to be at least as effective and well tolerated as intranasal beclomethasone in the treatment of seasonal allergic rhinitis, providing at least comparable relief from all nasal symptoms including congestion and significantly greater relief from ocular symptoms than the topical steroid.