Human placental cord blood includes many different types of stem cells, the majority being hematopoietic cell progenitors. Aldehyde dehydrogenase (ALDH) is a cytosolic enzyme responsible for the oxidation of aldehydes. As progenitor cells express markedly high levels of ALDH compared to differentiated cells of numerous types, ALDH activity has been valuable as a functional marker to identify progenitor/stem cells. In order to develop cord blood stem/progenitor cell therapeutic preparations, we examined the potential of short term storage of human umbilical cord blood without freezing the cord blood unit. Cord blood was stored at 4oC as either whole blood or as a mononucleated cell fraction isolated using Ficoll density gradient media. Using multicolour-labelling flow cytometry, we examined the total number of viable cells staining positive for ALDH(br), CD34 and CD45 cells in the cord blood preparations stored cold up to 4 days without freezing. Results indicated that ALDH(br) positive cells that were rich in CD34+ and CD45+ cell populations were able to adapt and survive with a higher rate of viability at 4oC without the need for freezing compared to non-progenitor cells.