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The Hydrological Simulation Program-FORTRAN (HSPF) describes volume-dependent discharge from a stream based on stage, surface area, volume, and discharge entries in a function table (FTABLE). This paper examines HSPF flow predictions simulated using FTABLEs generated from field and computer-based data sets. The study area is the 906 km Pigg River watershed, located in southern Virginia. Cross-sectional profiles spaced at defined intervals along the streams were obtained during field surveying and processed to create four sets of field-based FTABLEs. Geographic Information System (GIS) Digital Elevation Models (DEMs) and Natural Resource Conservation Service (NRCS) bankfull equations were used to create a fifth, computer-based set of FTABLE inputs. A comparison of FTABLEs showed similarities in stage-discharge curves for the bankfull range and differences at floodplain depths. The Smirnov k-sample test was used to compare flow rates simulated by HSPF using these FTABLEs. No significant difference was found (p=0.99) among the HSPF outputs from all five scenarios. Evaluation also demonstrated that the number of simulated cross-sections per stream reach used to generate FTABLEs minimally affected flow predictions. Therefore the more efficient computerized data are a viable option for simulations requiring only accurate predictions of flow rates from HSPF.