In a 1-year, placebo-controlled, double-blind, randomized study the long-term effect of Fluticasone Propionate Aqueous Nasal Spray (FPANS) in 42 patients with a perennial allergic rhinitis was studied with regard to safety and efficacy. Twenty-nine patients completed the entire treatment period. After 1 year of treatment no deleterious changes consequent on therapy were observed in nasal mucosal biopsies. The appearance of the epithelial layer, the degree of cellular infiltration, the extent to which the sinusoids were dilated and the degree of tissue oedema improved or remained unchanged in 93% of the patients of the FPANS group, versus 75% of the placebo group, and worsened in 7% of the FPANS group versus 25% of the placebo group. Assessment of the changes in haematological, biochemical, urinary, plasma cortisol levels, and in the findings during nasal examination revealed no significant differences between the two treatment groups. After 1 year of treatment symptom scores for sneezing, nasal itching, and total symptom score were significantly better in the FPANS treated group (P < 0.05, P < 0.05, P < 0.01). An initial reduction in total symptom score was found after 4 weeks FPANS treatment with a further reduction after 8 months of FPANS treatment. These findings suggest that the maximum efficacy of topical intranasal steroids is reached after long-term treatment, and thus advocates longer usage before treatment is stopped because of presumed inefficacy.