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Watershed and water quality-based assessment and integrated analysis of point and nonpoint sources are increasingly emphasized by USEPAs water program staff and their counterparts in states and pollution control agencies. BASIN 3.0 (Better Assessment Science Integrating Point and Nonpoint Source) is a system developed to meet the needs of such agencies. This study was conducted to evaluate the major watershed-scale models, SWAT (Soil and Water Assessment Tool) and HSPF (Hydrological Simulation Program-FORTRAN), included within BASINS 3.0 system. SWAT and HSPF were calibrated and validated for the baseline condition within the Upper North Bosque River Watershed (UNBRW), an intensive dairy producing region located in central Texas. The baseline condition within UNBRW was simulated from 1988 through 1999, and model output was calibrated for flow, sediment, and nutrients measured from five stream sites within the UNBRW for the period of January 1994 through June 1995 and validated for the period of July 1995 to July 1999. SWATwithin BASINS 3.0 was more user friendly than HSPF. The predicted flow and sediment by HSPF was closer to measured value especially during validation period. However, SWAT had better prediction of nutrient loading during calibration and validation periods.