Morbidity, hospitalization, and mortality associated with aspiration pneumonia are chief among the concerns of clinicians and researchers working with individuals with dysphagia. Conventional wisdom continues to hold that aspiration of any material into the lungs can lead to aspiration pneumonia. While many questions remain regarding the pathogenesis of aspiration pneumonia, a number of studies have suggested that pulmonary aspiration of differing materials may not present an equal risk for the development of aspiration pneumonia. Olson (1970)  found that aspiration of water in the rabbit lung is less injurious to the pulmonary system than milk or a 5% glucose solution in water. Later, Splaingard, Hutchins, Sulton, and Chaudhuri (1988)  suggested that pulmonary aspiration in humans is common and usually well tolerated. Schmidt, Holas, Halvorson, and Reding (1994)  reported aspiration of thicker fluids and semi-solids was predictive of aspiration pneumonia and death. In that study, the odds ratio was 5.6 times greater for the development of aspiration pneumonia and 9.2 times greater for death in those who aspirated thickened liquids or more solid consistencies when compared to those who did not aspirate or who aspirated thin liquids only. Similarly, Holas, DePippo, and Reding (1994)  reported that aspiration pneumonia risk was significantly greater if thick liquid or more solid consistencies were aspirated. Feinberg, Kneble, Tully, and Segall (1990)  stated that aspiration of water was benign. Later, Feinberg, Kneble, and Tully (1996)  reported that the frequency of aspiration pneumonia did not differ significantly between patients who aspirated thin liquids and those who did not aspirate.