A method for purifying CSF protein is described. The method comprises: precipitating the protein with ammonium sulfate at 80% saturation to form a pellet containing the CSF protein; resuspending the pellet in a buffered solution at a pH in the range of about 6 to about 8; applying the buffered solution containing CSF to a chromatographic column, eluting with the buffered solution containing sodium chloride and collecting the fractions having CSF activity; pooling the active fractions, applying them to a C4 reverse phase column and eluting with a 0 to 90% acetonitrile gradient to collect the active fractions. The purified CSF protein has a specific activity of at least about 1.times.10.sup.7 units per mg of protein and preferably at least about 4.times.10.sup.7 units per mg of protein when assayed using the human bone marrow assay.