Global and regional climate models are valuable tools for assessing the effects of natural and anthropogenic perturbations to climate and hydrology. Results of a coupled regional climate and hydrologic model system, designed for the integrated assessment of climate-hydrologic impacts at regional scales demonstrate that (a) simulated precipitation in a storm event is sensitive to the spatial resolution of the regional climate model and (b) spatial variability of precipitation and hydraulic variables must be accounted for in order to realistically capture the basin-scale hydrologic response to a storm event. The regional climate model (with a spatial resolution of 4 to 36 km) can be driven either by global climate model output (with resolutions at the order of 100 km) or by observed climate data. The meteorological fields simulated over the mid-Atlantic region of the USA were disaggregated to drive the basin-scale hydrologic model (with a resolution of 1 km). With the improved treatment of spatial variability, the simulated streamflow at the basin outlet compares well with observations. These results from coupled climate-hydrologic models at regional scales suggest that climate-hydrology modeling studies that do not allow for spatial variability may be misleading. ¿ 2000 American Geophysical Union