In a double-blind trial thirty-five patients with moderately-severe nasal polyposis were treated with intranasal beclomethasone dipropionate aerosol for 3 weeks. The dose given (400 mug/day) had only local effect on the symptoms. Judged by diary card scores the nasal symptoms were reduced to 52% of the pre-trial level for the whole group. Corrected for the placebo effect the percentage was 68. The reduction of symptoms was equally apportioned to the three symptoms, sneezing, nasal secretion and blockage. The treatment was tolerated well, and it is concluded that intranasal treatment with beclomethasone dipropionate aerosol offers most patients with nasal polyps a good response without any risk of systemic steroid side-effects.