The clinical efficacy and side effect of (1) beclomethasone dipropionate aqueous nasal spray, 400 micrograms daily, (2) astemizole, 10 mg daily, and (3) beclomethasone, 400 micrograms, plus astemizole, 10 mg daily, were compared in a double-blind, randomized, parallel-group trial. Ninety adults were matched into groups of three according to sensitivity to ragweed pollen. One of each of the three subjects was assigned to nasal spray alone, one was assigned to astemizole alone, and one subject was assigned to both medications. Medications were started 1 week before and continued daily until 1 week after the ragweed-pollen season (6 weeks). If rhinoconjunctivitis was inadequately controlled with the trial medications, pressurized steroid nasal spray and/or antihistamine-decongestant eye drops were used in the minimum dose that would ensure relief. Nose and eye symptoms and concomitant medication use were recorded daily in a diary. Sneezing, nasal obstruction, and rhinorrhea were significantly better, and less additional nasal spray was used in subjects taking beclomethasone alone than in subjects taking astemizole alone. Beclomethasone plus astemizole provided no better control of rhinitis than beclomethasone alone. Eye symptoms and eye drop use tended to be less in subjects taking astemizole alone than in subjects taking beclomethasone alone, but the best control of eye symptoms was recorded in the subjects taking both trial medications. Side effects were mild or transient.