The invention relates to a method of preparing an intra-dermally, intra-articularly, sub-dermally or topically administrable growth factor concentrate derived from human platelets. The method comprises the steps of suspending human platelets in multiple electrolyte isotonic solution; snap-freezing the suspension; thawing the frozen suspension; and sterile-filtering the suspension. In particular, in this method, a fixed number of platelets is suspended in a fixed volume of multiple electrolyte isotonic solution to obtain the required concentration of growth factors in the growth factor concentrate, snap-freezing of the suspension is carried out at a temperature of −120° C. to −200° C., thawing of the frozen suspension is carried out at 25° C. to 37° C., and cellular debris are separated from the thawed suspension and the resultant suspension of growth factors is diluted with an isotonic medium before sterile-filtering.