In the last decade, there has been renewed interest in the use of granulocyte transfusions to treat infections in individuals with compromised immune systems. However, granulocytes only remain functional for about a day after isolation and this short shelf life is a significant drawback. Cryopreservation would allow long term storage of granulocytes, but an effective cryopreservation method is currently unavailable. The following study was performed to provide membrane permeability values for multiple cryoprotectants in hopes of aiding the optimization of cryoprotectant addition and removal and minimizing the detrimental effects of the process. The granulocytes were separated from whole blood using centrifugation with Polymorphprep as the separating agent. The cellular membrane permeability values were then measured using a Beckman Coulter Counter Multisizer 3 under custom setup conditions. The cryoprotectants studied were glycerol, DMSO, ethylene glycol, and propylene glycol at the respective total concentrations of 1, 2, 2, 1 Osm/kg at temperatures of 4, 21, and 37 °C. The resulting membrane solute permeability values at 20 °C reference temperature for DMSO, ethylene glycol, glycerol, and propylene glycol were respectively 5.96, 7.84, 0.950, and 3.45 um/min and the Arrhenius activation energies were respectively 60.4, 58.7, 68.2, and 62.3 kJ/mol. The resulting hydraulic permeability values in the same order and temperature were 0.196, 0.189, 0.259, and 0.113 um/(atm min) and the Arrhenius activation energies were respectively 56.3, 60.7, 68.5, and 47.1 kJ/mol. It is anticipated that these permeability values will aid in the development of successful cryopreservation procedures for granulocytes. / Graduation date: 2013