The short-term effects of local intranasal administration of fusafungine were studied for its anti-inflammatory and antimicrobial properties against experimentally induced bacterial rhinosinusitis. The maxillary sinuses of 20 rabbits were infected with encapsulated Streptococcus pneumoniae after mechanical occlusion of each animal's anatomic ostium. Either fusafungine solution or placebo was administered as a nasal spray through the nostrils twice daily for 10 days. Histopathological grading of inflammation, biochemical assay of inflammatory mediators, and the number of bacterial species isolated from the nasal cavities all showed significant recovery from inflammation after fusafungine treatment. The beneficial effects of fusafungine on inflamed sinus mucosa may possibly also be attributable to an initial alleviation of inflammation in the nasal cavity, which permitted entry of the drug to the sinus cavity through a partially reopened ostium. A reciprocal relationship between nasal and sinus reactivity involving generalization of inflammation and recovery was also thought to be of importance. The present findings indicate that local applications of fusafungine may effectively improve clinical conditions producing rhinitis and sinusitis.