Preparation of monodispersed inorganic-organic hybrid particles has become one of the most attractive research topics in recent years. In this study, phenylsilsesquioxane (PhSiO3/2) particles were synthesized from phenyltriethoxysilane (PhSi(OEt)3), ethanol (EtOH), hydrochloric acid for hydrolysis and ammonia water for polycondensation by the sol-gel method. Spherical PhSiO3/2 particles were obtainable by varying the mole ratios of EtOH, H2O, HCl and NH3, to PhSi(OEt)3. The particle size was changed from 0.1 to 5.0 .m with the mole ratio. Under the optimum conditions, monodispersed particles with 1.50 .m in diameter and 0.05 of normalized standard deviation were successfully prepared.