Dielectric properties of pure, unsintered and pressed barium ~tanate were investigated: The .initial nonlinear variation of dielectric constant and dissipation factor with temperature observeds attrI but.ed to the water vapor adsorbed on the surface exposed to the pores. The absence of ferroe.lectnc propertIes and the linearity in dielectric constant and dissipation factor with temperature found in a heat-teated sample are explained on the basis of a nonferroelectric surface layer. This was supported by the experiment showing the decrease in dielectric constant with decreasmg partIcle size.