A double-blind, cross-over comparison of flunisolide nasal spray and its inactive aqueous vehicle has been carried out in fifty patients suffering from perennial allergic rhinitis. Patients were randomly allocated to two groups; the first group (group I) received flunisolide for 3 weeks and then placebo for 3 weeks while the regimes were given in the reverse order to the second group (group II). Patients used two insufflations of 0.1 ml in each nostril twice daily. As the active spray was presented as a 0.025% solution of flunisolide, the total daily dosage was 200 μg. Patients were assessed on admission and at the end of each 3 week period. The results show flunisolide to be significantly superior to placebo in relieving sneezing, nasal obstruction and postnasal drip, as well as improving the quality of sleep and everyday life. At the end of the trial the preferences for treatment recorded by both doctors and patients were significantly in favour of the flunisolide spray. Side effects were minor and occurred during both placebo and active phases of the trial. A short Synacthen test performed at each visit showed no evidence of adrenal suppression.