The dielectric constants of some aqueous-organic solvent mixtures have been analysed by an equation analogous to Grunberg and Nissan equation. The hydration numbers are found out at the maxima and minima of the plots of Δϵ versusx2. The extent of hydration of organic solvents is discussed in the light of structure of the solvents. It is shown that the equations can be very well applied to aqueous-organic solvent mixtures. An interaction parameterdis defined to fit the dielectric constant data of the mixtures which bears a linear relationship with ϵ2.