Hydrocarbons which enter the subsurface through spills or leaks may create serious, long-lived ground-water contamination problems. Simplified models of the separate phase flow of the hydrocarbon and its dissolution into ground water may be appropriate for gaining insight into the significant phenomena, emergency response, or generic simulation for regulatory development. The paper outlines the components of a set of screening models for this problem and focuses on parameter sensitivity. Tabulated values of soil properties are used to model releases in typical soil materials. The availability of standard deviations of parameter values allows assessment of model response with regard to typical parameter variability. This knowledge has important consequences for emergency response applications which tend to rely on tabulated data instead of site specific data. Ultimate interest usually lies with dissolved aqueous concentrations, so the parameter sensitivity is assessed through concentrations predicted for down-gradient wells, as well as other significant aspects of the model results.