In the present paper some aspects of the thermodynamics of a fluid-saturated porous solid, taking into account the phase change of liquid into gas, are discussed. Based on the principles of the thermodynamics of irreversible processes, restrictions for the constitutive equations of the constituents are developed, in particular for the phase transition. The porous body is assumed to be incompressible and elastically deformed, and the pore space is filled with an immiscible liquid-gas mixture (moisture). The theory presented here provides some background that can be found suitable, e.g., for drying aspects.