Groundwater contamination from hydrocarbon spills or leaks is a widespread problem. When the volume of released product is small and/or the depth to groundwater is sufficiently great, all of the nonaqueous phase liquid (NAPL) may be retained in an immobile condition in the unsaturated zone by capillary forces. For larger spill volumes or shallower water tables, NAPL may reach the groundwater where it will spread laterally if its density is less than water. Such light NAPL include most crude oils and refined hydrocarbons, e.g., gasoline, wet fuel, and fuel oil. A practical algorithm for estimating capillary pressure parameter (α) from total petroleum hydrocarbon (TPH) measurements in contaminated soils was presented. The procedure was based on computing the fluid saturations in soil from TPH measurements assuming an empirical model for capillary pressure-saturation relationship. Accurate estimates of α were obtained utilizing the algorithm for homogeneous and moderately heterogeneous soils. However, accuracy in the estimates of α decreased with increasing soil heterogeneity. Close agreement between measured TPH data and TPH values computed using the proposed algorithm demonstrated the practical utility of the approach.