The solubility of toluene, ethylbenzene, and propylbenzene in water was measured over conditions of 0.10-400 MPa and 273.2-323.2 K. Solubility was found to initially increase with increasing pressure and then decrease from a maximum at around 100 or 200 MPa. On the other hand, the solubility-temperature curve at 0.10 MPa exhibited a minimum at around 290 K. The solubility minimum of toluene disappeared at high pressures. The overall solubility-pressure-temperature surface resembles a portion of a distorted hyperboloid. The partial molar volume of these solutes in water was estimated from the pressure coefficient of solubility using the compression of the solutes in the pure liquid state, a property that was also measured in the present study. Expansion coefficient and isothermal compressibility of partial molar volume of hydrophobic groups in water at atmospheric pressure are estimated from literature data. The expansion coefficient of partial molar volume was found to be significantly larger at atmospheric pressure than at high pressure. Partial molar volume in the low-temperature region was found to increase with increasing pressure and then to decrease at pressures over ca. 100 MPa, resulting in a maximum. However, the maximum was found to disappear in the high-temperature region, where the volume decreases regularly. This behavior can be ascribed to a unique property of pure water: the compressibility of water increases with decreasing temperature, or the expansion coefficient increases with increasing pressure in the range of pressure and temperature in the present study. Such a unique property seems to weaken or disappear in the water under hydrophobic hydration.