A fully three-dimensional model of variably saturated flow on a hillslope has been used to explore the effects of different random patterns of saturated hydraulic conductivity on a 150 m by 100 m hillslope. Both surface and subsurface runoff production are simulated. The model's simulations suggest that peak discharges and runoff volumes are generally increased by the presence of heterogeneity, increasing with increasing variance and spatial dependence of the underlying random field. Simulations using different realizations with the same random field parameters show that for the case of soils showing no dependence, differences in runoff production between realizations are small at this scale of hillslope. The differences increase with increasing spatial dependence, particularly for the case of low-conductivity soils producing surface runoff.