This chapter deals with the volumetric (pVTx) properties of binary and ternary aqueous systems containing ionic and/or molecular solutes. It's main objective is to overview techniques for high temperature and pressure measurements and to provide compilation and assessment of all literature sources presenting experimental results reaching above 100°C. At the same time it is shown how to evaluate the volumetric functions of direct thermodynamic interest from the experimental results, how their temperature, pressure and concentration dependence is interpreted by theory, and what are the models of their correlation. Although the mixtures where the concentrations of constituents change from one extreme to another (“full range data”) are included the main focus is on systems (solutions) where water is a dominating component.