It is reported that the critical loci of the fluid He-H2O mixture exhibits maximum values in both temperature and pressure. This kind of behavior, never found before, was predicted by van der Waals for mixtures exhibiting immiscibility of the first kind. Results are obtained using a theoretical approach that takes into consideration the polarizability of the two components. Further, calculations for both isotherms and isobars show this kind of fluid phase behavior, as recently found experimentally. Since no temperature maximum was shown when using a nonpolarizable molecular model, the new result may be attributable to the polarizability of molecules. (C) 1997 American Institute of Physics.