A method is provided for use with extracted blood, including (a) applyingblood to a first gradient suitable for selecting first-pass cells having adensity less than 1.077 g/ml； (b) applying the first-pass cells to a secondgradient suitable for selecting second-pass cells having a density between1.055 and 1.074 g/ml； (c) increasing the number of cells having a densitybetween 1.055 and 1.074 g/ml, by culturing the second-pass cells for a periodlasting between 3 and 30 days； and (d) identifying endothelial progenitorcells in the cultured cells. Other embodiments are also described.
