The accumulation of food debris in the buccal vestibule surrounding a mandibular denture flange was studied. This investigation focused on the effect of the thickness, physiologic molding, and slope of the buccal flange of denture base on the patient's ability to expel test-food particles from the area. Experimental denture bases were placed in the mandibular buccal vestibule of subjects having a complete natural dentition. Only the slope of the polished surface of buccal flange was found to have a significant positive correlation with the ability to expel test food from the buccal vestibule.