A medical food was formulated as a dry powder product containing free essential amino acids, fat and carbohydrates. Samples were stored at 4°C, 25°C, and 40°C and evaluated periodically during storage. Proximate analysis, pH, amino acid analysis, osmolarity, emulsion stability, Hunter color difference, and sensory evaluation tests were performed. Changes could not be detected by the chemical tests employed, but were manifested in sensory analysis. This study indicated that sensory testing of medical foods is a critical tool in the assessment of product stability and must be considered an integral part of any medical food stability program. Chemical analysis alone will not provide sufficient data to allow prediction of either patient acceptance or product integrity.