Magnetite nanoparticles coated with tyrosine and histidine were synthesized by in situ decomposition of the precursors-coordination compounds containing the aminoacids as ligands. All of the obtained compounds were characterized using infrared spectroscopy (FTIR), X-ray diffraction, Mossbauer spectroscopy, magnetic and thermal measurements. Data demonstrate the presence of the aminoacids chemisorbed on the surface of magnetite nanoparticles and their superparamagnetic character. (C) 2008 Elsevier B.V. All rights reserved.