The primary goal of the Ninth Industrial Fluid Properties Simulation Challenge was to test the ability of molecular simulation methods to predict water/oil interfacial tension at conditions of high temperature and pressure. The challenge focused on three oils: n-dodecane, toluene, and a 50:50 by weight blend of dodecane and toluene. A set of experiments were performed with a pendant drop tensiometer to establish the benchmark data to be used to judge the challenge, and these data were unavailable to the challenge entrants until after they had submitted their predictions. Among the three oils, dodecane exhibited the highest interfacial tension and strongest dependence of interfacial tension on temperature. The water/oil interfacial properties for the blend were much closer to those of toluene than dodecane, indicating the interface in the case of the blend may be enriched in toluene compared to the bulk composition of the blend. (C) 2018 Elsevier B.V. All rights reserved.