In order that the entries in the first industrial fluid properties simulation challenge could be judged, a benchmarking committee comprised of the authors of this paper was established. The mandate of the committee was to determine best values for the physical property questions posed in the challenge based on a thorough evaluation of the available literature and on new experimental measurements, as necessary. A key part of the activity was to determine robust estimates of uncertainty for the benchmarks, as these also played a role in the evaluation of challenge entries. (C) 2003 Elsevier B.V. All rights reserved.