Accurate predictions of the mutual solubility of water and hydrocarbon fluids are important in exploration and production of hydrocarbon reservoir fluids. This paper presents experimental phase equilibrium data for a system consisting of water and a as condensate mixture from a high temperature and high pressure reservoir in the North Sea. The phase equilibrium measurements were undertaken at temperatures of 35, 120 and 200 degreesC and pressures of 700 and 1000 bar. The data show that the mutual solubility of water and the petroleum reservoir fluid is quite considerable at high temperatures and pressures. It is further shown that the measured data can be modeled by use of the Soave-Redlich-Kwong (SRK) equation with the non-classical mixing rule of Huron and Vidal.