Because the upper airway is partially enclosed in a rigid boundary, enlargement of soft tissue structures within this boundary could narrow the airway. The purpose of this study was to determine whether enlargement of the soft tissue space in the region of the lateral pharyngeal fat pad would increase pharyngeal resistance and narrow the retropalateal upper airway. In five young male anesthetized pigs, we inserted balloon occlusion catheters in the lateral pharyngeal fat pad under computerized tomographic scan guidance. We measured pharyngeal resistance with a pharyngeal catheter and a tightly fitting face mask before and after inflation of the balloons. We also measured pharyngeal airway cross-sectional area before and after inflation of the balloons. In all pigs, balloon inflation significantly increased pharyngeal resistance and significantly decreased the area of the retropalateal airway. We conclude that enlargement of the soft tissue space in the region of the lateral pharyngeal fat pad increases pharyngeal resistance and narrows the retropalateal airway in anesthetized pigs.