The purpose of this study was to investigate comparability of viscosity of liquids used in assessment and treatment of infants with dysphagia. Goals of this study were as follows: (1) Establish baseline viscosity values for (a) the commercial barium assessment liquids of varying thicknesses and (b) clinically typical infant formula thickened with varied thickeners. (2) Compare the baseline viscosities of the various liquids for correlation of values. We attempted to mimic real-world situations and recreate clinical assessment and treatment conditions. We also identified and made every effort to control typical clinical variables, e.g., mixer and mixing procedure, brand of product, and temperature of liquid. The method of measurement was based on rheologic principles and used a Brookfield Engineering LVDV II + Pro Cone/Plate Viscometer at spindle and speed combinations to maximize shear rates consistent with swallowing. Statistically, there was no comparability between barium and formula mixtures, regardless of thickener utilized. The implications of these findings and the need to develop a standardized means of thickening formula to a viscosity comparable to the assessment materials are discussed.