The unified theory of electrolytes (J. Phys. Chem. B 2009, 113, 2398-2403) is used for the prediction of the standard state partial molar volumes of aqueous chlorides and hydroxides of the alkali metals, alkali earth metals, and the first row transition metals to high temperatures and pressures. The only required input to the model is the thermodynamic properties from reference tables at 298.15 K and 0.1 MPa. Comparison of the predicted values for the standard state partial molar volumes of aqueous electrolytes from this study with the available experimental data indicates good agreements to well within the combined uncertainties of the experimental data and the present model up to 623.15 K and 400 MPa. The present model is also compared with the correlations of Sedlbauer-O'Connell-Wood (SOCW) and the revised equation of Helgeson, Kirkham, and Flowers (HKF), which has been incorporated in the SUPCRT92 software.