This study examines the role of cavitation in drying cementitious materials. Classical nucleation theory is used to understand and study the parameters that influence cavitation pressures. The water desorption isotherms indicate that both heterogeneous and homogeneous cavitation occur during the drying of saturated cement pastes and the commonly observed large moisture loss at 0.3 pv/psat can be explained by homogeneous cavitation. The homogeneous cavitation is suggested to occur in the gel porosity of the inner product that is accesible by the interlayer spaces. The findings of this study indicate that it is important to consider the effects of cavitation for characterization of pore sizes from moisture desorption isotherms.