This paper concerns with the behavior of an electrodeionization (EDI) system for concentration of citric acid from fermentation broth. Commercially cation-exchange membrane (MC-3470) and anion-exchange membrane (MA-3475) were used as ionic selective barriers of the EDI stack. The diluted compartments of the EDI stack were filled with mixed ion-exchange resins (purolite strong acid cation-exchange, C-100E and strong base type I anion resins, A-400). The experiment used feeds with citric acid concentration in the range of 500-10,000 ppm and feed flow rate in the range of 1-41h(-1). The V-I characteristics indicated that there were essential differences in current transport and electrical resistance between the EDI and the electrodialysis (ED) processes. Moreover, the overall current efficiency was in the range of 40-96% and has been found to be a function of feed concentration and current density. The performance of the EDI system was also stable during 24 h operation. (C) 2004 Elsevier B.V. All rights reserved.