This Standard Operating Procedure (SOP) is based on the Vanderbilt Human Islet Phenotyping Program (HIPP) procedures for dispersing islets to single cell suspension and quantitatively assessing viability by Trypan Blue staining. This SOP defines the assay method used by the Human Islet Phenotyping Program (HIPP) for quantitative and qualitative determination of the Purified Human Pancreatic Islet product, post-shipment, manufactured for use in the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)-sponsored research in the Integrated Islet Distribution Program (IIDP).