Beclomethasone dipropionate as a pressurized aerosol is effective in nasal polyposis, but the efficacy is only moderate. In these partly-blocked noses, it seems possible that the insufflated drug in powder form is better distributed over the mucous membrane than the pressurized aerosol. To test this hypothesis, we treated forty-two patients with nasal polyposis with intranasal beclomethasone dipropionate as a powder and as a pressurized aerosol in a double-dummy, cross-over design. There was no difference between the treatments in sixteen patients, while in twelve cases there was a preference for beclomethasone dipropionate as aerosol, and in fourteen, for the powder form. Fourteen found the aerosol most irritating and nineteen, the powder. Thus, in a group of polyp patients there were no significant differences between the two application forms, but possibly there is a need for both aerosol and powder, as there appeared to be differences in the individual responsiveness to the two types of intranasal medication;. Blind microscopy of wiped nasal-smears before and after beclomethasone dipropionate treatment showed a reduction of basophilic cells, and counting of sneezes after medication demonstrated a reduction in the number of sneezes. These results suggest that a reduction of epithelial mediator-cells and of irritant receptor-sensitivity are of importance for the efficacy of topical steroids in rhinitis.