The need for sophisticated component therapy has resulted in improved techniques for obtaining concentrates of platelets and granulocytes. The use of single donors as a source for these products is advisable to avoid multiple sensitizations. A method for obtaining large quantities of platelets has been established rather easily. Obtaining concentrated granulocytes represents a greater problem owing to the difficulty in separating granulocytes from red cells by differential centrifugation or sedimentation since the specific gravities are similar. Separation is easier by the use of hydroxyethyl starch. A modified solution of hydroxyethyl starch and sodium citrate was used with good results.