Platelets prepared by discontinuous flow centrifugation contain significant numbers of leukocytes and red cells. Platelet products often are centrifuged further to remove this cellular "contamination." A method is described by which platelet products obtained by cytapheresis were prepared using an additional slow centrifugation step (121 X g for 7.5 minutes). In a production environment, we removed an average of 97 percent of leukocytes and most of the contaminating red cells with this method, while retaining 89 percent of the platelets in the final product. This method is an improvement over methods described previously and was consistently effective in routine use.