Using titanium tetrachloride (TiCl4) as a precursor, titania (TiO2) nanoparticles were synthesized in the diffusion flame (DF) of air and liquid petrol gas (LPG). The effects of air and LPG flow rates and flow ratio, flame temperature and flame shape on the synthesized titania nanoparticles were investigated. Experimental investigation showed that the mean particle size of TiO2 increased obviously with increasing airflow rate, and not obviously with that of LPG, the mean particle size at optimal experimental condition was less than 20 nm, the rutile fraction in the synthesized powder increased with increasing flame temperature and the particle size was affected by the flame height. A particle-dynamic model, describing the nucleation and coagulation of titania monomers/nanoparticles, was used to account for the experimental results based on the isothermal assumption. Generally speaking, the calculated particle sizes from the particle dynamics were consist with the experimental measurements, especially, when the feed concentration of TiCl4 was low. (c) 2005 Elsevier B.V. All rights reserved.