The COSMO-RS method in its COSMOtherm implementation has been used to predict the vapor liquid equilibria of problem sets 1a and 1b of the first industrial fluid property prediction challenge, i.e. for the mixtures of dimethylether (1) and propene (2) and of nitroethane (1) and propylene glycol monomethyl ether (1-methoxy-2-propanol) (2). Good quality predictions for both systems have been achieved within less than one day of work, using experimental values for the pure compound vapor pressures and predicted activity coefficients for the mixture thermodynamics. In addition to the results reported for the challenge predictions based on predicted pure compound, vapor pressures are reported and discussed in this paper. (C) 2003 Published by Elsevier B.V.