The effect of pressure on the volume of tetrahydrofuran (THF) has been measured as the ratio of the volume under pressure to its value at 0.1 MPa pressure with a bellows volumometer for temperatures from T = (278 to 323) K at pressures up to 300 MPa. Similar measurements have been made for two of its mixtures with water, x(THF) = (0.25 and 0.5) for temperatures from T = (288 to 338) K. The data have been fitted with two equations of state. Densities at atmospheric pressure have been measured for THF and for aqueous mixtures of THF. For the latter the densities cover the composition range (0.2 less than or equal to x less than or equal to 0.8) at the temperatures (288, 298, and 313)K and smaller ranges of composition at higher temperatures. Isothermal compressibilities, volume fluctuations, thermal expansivities, and the change in isobaric heat capacity from its value at 0.1 MPa pressure have been calculated. Significant features on these properties are discussed.