Flow calorimetric measurements of the excess molar enthalpy H-m(E) of {xH(2)O+(1-x)C6H6} measured at the pressure 16.4 MPa are reported. Measurements made at the temperatures (503, 521, 544, and 560) K are in a region of the phase diagram which shows partial miscibility of the two liquids. Measurements made at the temperatures 576 K and 581 K are in a homogeneous fluid region, and measurements made at T = 592 K cross a liquid-vapour two phase loop at x > 0.75. The H-m(E)(x) diagrams all show linear behaviour where two phase regions are crossed, and the extrema of these linear sections gives information about the location of phase boundaries. Values of H-m(E) at x = 0.5 are shown to lie on curves which are a continuation into the liquid phase region of vapour phase H-m(E) (x = 0.5) measurements published previously. The measurements are compared with the cubic equation of state of Patel and Teja. The equation generates H-m(E)(x) isotherms which have the correct shape and which are closer to the experimental measurements at high temperatures than at low temperatures.