A new group contribution method for calculating the heat of vaporization DELTAH(V) of pure substances based on UNIFAC is presented in this paper. The UNIVAP (UNIversal heats of VAPorization) method permits this calculation over a wide temperature range with high accuracy. A mean relative deviation of 1,25 % was found. A sound theoretical background enables good predictions. The parameters were simultaneously fitted to a large number of DELTAH(V) data, using the Thermodynamic Data Base (TDB).