In this paper densities for THF (tetrahydrofuran) and THF + water mixtures measured with the help of the Anton Paar DMA HPM vibrating tube densimeter ale reported. The pure component densities of tetrahydrofur an measured in the temperature range from 278 to 437 K and pressures up to 130 MPa were correlated with the TRIDEN-System Additionally densities of the binary mixture tetrahydrofuran + water were measured for 6 different concentrations in a temperature range from 288 to 338 K and up to 130 MPa Excess volumes (nu(F)) of the mixture were determined using the own con elation of the tetrahydrofuran densities and the equation of state (EoS) for water by Wagner and Pruss. Redlich-Kister polynomials were used to fit the nu(E)-data. Additionally in this work it was checked if the vibrating tube densimeter allows the determination of the miscibility gap for the system THF-water as a function of temperature and pressure (C) 2010 Elsevier B V. All rights reserved