Spherical particles constituted by nanocrystals of titanium oxide TiO2 have been prepared through reactive microemulsion precipitation. A water-in-oil microemulsion. added with a suitable emulsifier, has been used. The effect of the process parameters (water to oil ratio, type and amount of surfactant, concentration of precursor solution, mixing velocity) on the final characteristics has been investigated, in terms of structural phase and particle size. The titania nanopowders were characterized by means of X-ray diffraction, thermogravimetric and differential thermal analyses and scanning electron microscopy. The results obtained by different process conditions showed the development of both titania rutile and anatase spherical particles, with particle size ranging from tens to hundreds of nanometers. (C) 2008 Elsevier B.V. All rights reserved.