50 patients with chronic mucopurulent rhinosinusitis were randomly allocated to treatment with nasal sprays of dexamethasone, tramazoline, and neomycin, dexamethasone and tramazoline with no antibiotic, or matched placebo (propellant alone) four times daily to both nostrils for 2 weeks. The patients were assessed in a double-blind manner for symptomatic response and improvement in nasal mucociliary clearance, nasal airway resistance, sinus radiographs, and intranasal bacteriology and appearance. Both active preparations (with antibiotic 14 of 20 patients responded; without antibiotic 12 of 20 patients responded) were more effective than the placebo (2 of 10 patients responded). There was no significant difference in response between the active preparations with and without antibiotic. Thus, in treatment of chronic mucopurulent rhinosinusitis, reduction of the inflammatory response and decongestion make topical antibiotic unnecessary, probably by allowing host clearance mechanisms to recover.