Digital elevation models (DEMs) are representations of topography with inherent errors that constitute uncertainty. DEM data is often used in analyses without quantifying the effects of these errors. A method for simulating uncertainty that is implemented as an extension for the ArcView Spatial Analyst GIS environment was developed. Users can evaluate DEM uncertainty using DEM metadata and spatial characteristics of the DEM. Monte Carlo simulation techniques were used to represent DEM uncertainty and its effect on various topographic parameters (slope, aspect, upslope area, flow direction and the topographic index) often used in hydrologic analyses. Different methods for quantifying uncertainty were investigated.