Pressure perturbation calorimetry (PPC) is a relatively new calorimetric technique which allows us to investigate volume behavior of solute molecules in aqueous solutions or colloidal particles in aqueous dispersions. This article deals with the application of the PPC technique to phospholipid vesicle dispersions along with a brief description about the theoretical aspect of this technique on the basis of our recent studies on the volume and relaxation behavior of phospholipid bilayers.