Four protein concentration methods, applicable to cerebrospinal fluid, were compared in order to choose a procedure that not causing protein denaturation, is accurate, precise and easy to perform in routine laboratories. The studied methods were: dialysis against arabic-gum solution, centrifuge-ultrafiltration, absorption of low molecular weight substances by dry polyacrylamide gel and pressure ultrafiltration. Blood serum was diluted, then concentrated by these procedures and analyzed by cellulose acetate electrophoresis; the undiluted serum served as control. It was observed that two methods: pressure ultrafiltration and absorption of low molecular weight substances by polyacrylamide hydrogel, are not suitable for concentrating diluted fluids because they frequently cause protein denaturation. It was concluded that dialysis against arabic-gum is the most suitable, of the methods studied, for application in routine laboratories taking in account that this procedure is precise, relatively accurate, simple and of low cost.