Magnetic nanocomposite thin films formed by nickel ferrite particles dispersed in silica matrix have been prepared by sol-gel process. The starting solution was prepared using tetraethylorthosilicate (TEOS) as a precursor of silica, and metallic nitrates as precursors of the ferrite. NiFe2O4/SiO2 films were prepared with 5-30 wt.% ferrite contents and deposited on glass, quartz and silicon plates using the dip-coating process. The films obtained were adherent, transparent, homogeneous, and free of microcracks, with thickness between 70 and 100 nm. The nanocomposite films presented the formation of crystalline NiFe2O4 nanoparticles measuring between 6 and 10 nm dispersed in amorphous SiO2 matrix and a saturation magnetization above 8 emu/g. (C) 2003 Elsevier Science B.V. All rights reserved.