We report the electrochemical properties of submicron-sized particles of NaFePO(4). Two materials have been studied and characterized by XRD, SEM, EDX, EIS and Raman experiments: the maricite phase synthesized by hydrothermal method and the olivine phase obtained from delithiation of LiFePO(4). NaFePO(4) materials have an electrochemical activity in Na cell using NaPF(6)-EC-DEC electrolyte, but only in the heterosite phase, and the capacity is reduced already in the second cycle. The two-phase system at intermediate compositions has also been analyzed. (C) 2011 Elsevier B.V. All rights reserved.