2-Mercapto-5-methylpyridine-N-oxide (MMPNO) and its sodium salt (NaMMPNO) were synthesized. The reaction of the latter with Fe3+ generates Fe(MMPNO)(3) chelate. The thermolysis of this chelate at 350 degrees C yielded highly pure reddish-brown gamma-Fe2O3 nanocrystallites with an average particle size of 6.2 nm, a particle size range of 4.2 to 14.8 nm, and a specific surface area of 51.5 m(2) g(-1). The thermolysis process was optimized using the 2(2) fractional design. Quantitative tests and characterization of products were carried out by UV-vis spectroscopy, XRD, LLS, SEM, TGA, BET, TEM, FT-IR, elemental microanalysis, and classical analytical measurements.