BaTiO3, SrTiO3 and (Ba1-xSrx)TiO3 fine particles were synthesized from amorphous TiO2 fine particles by a hydrothermal method. The relationship between the specific dielectric constant of the sintered disk and the mean size of composing particles has been investigated. The specific dielectric constants of the sintered disks of BaTiO3 and SrTiO3 particles attain values exceeding 6000 in the range of the particle size of 0.10-0.17 mu m. The specific dielectric constant for the sintered disk of (Ba1-xSrx)TiO3 particles synthesized at various atomic fractions of Sr (x) attains maximum values at both atomic fractions of 0.08 and 0.95. It has been suggested that the size of particles composing the disk should considerably affect the specific dielectric constant of the sintered disk.