The present invention relates to the isolation of human stem cells for use e.g. in cell therapy. More specifically, the invention is a method of separating mononuclear cells from human blood, which method comprises providing a human blood sample together with density gradient media (DGM) in a container; spinning the container comprising blood and DGM; and collecting the DGM fraction that comprises mononuclear cells; wherein the DGM has a density which is >1.080 and <1.090 g/cm3 as measured at 250C. The invention also relates to bags and tubes which contain density gradient media wherein the density and osmolality has been optimized for use in the present method, preferably as kits.
