A study of ninety-nine hay fever sufferers was conducted to compare the effect of treatment with flunisolide nasal spray plus terfenadine tablets with that of terfenadine alone. The study was carried out over an 11-week period, which covered the pollen season between May and August. All patients received 60 mg terfenadine twice daily and one group, of forty-nine patients, also received 50 mcg flunisolide to each nostril twice daily. Clinical assessments of nasal and ocular symptoms were made at admission and following 3, 7 and 11 weeks' treatment. An over-all evaluation of treatment effect was performed at each follow-up visit and nasal examination was carried out. Patients also completed diary cards daily. Both treatments were effective in reducing symptom severity, in comparison with previous seasons, but the combination treatment gave consistently better symptom relief. Statistically significant differences were detected in favour of the combined treatments group for nasal symptoms. Eye symptoms were found to be relieved to a comparable degree by both treatments. Results from daily patient self-assessments were consistent with these findings. The over-all evaluations by both patients and doctors were significantly in favour of flunisolide plus terfenadine. In conclusion, treatment of hay fever with flunisolide in addition to terfenadine was significantly more effective than treatment with the antihistamine alone.