The object of the profile accuracy study is to determine guidelines which indicate the effect of geometric accuracy and boundary roughness estimation on computed water surface profiles. To achieve this, an excess of 100 HEC -2 data sets have been collected from U.S. Army Corps of Engineers District and Division offices. These data sets provide the necessary information for computing steady state water surface profiles. The data sets were modified in several ways to obtain simple, clean data which represent general hydraulic conditions and not special, localized conditions. Also removed are any specialized options and associated data cards. The result is a data base of HEC-2 input data sets containing simple and concise information. These data sets are called the actual data sets. In addition to studying the effects of geometric accuray on computed profiles, HEC also evaluated the effects of the friction loss accuracy on profiles. The Manning's coefficient supplied with data sets are assumed to be the correct (or historically calibrated) values. The Manning's coefficients are then systematically changed to simulate errors in their estimation. A Monte-Carlo simulation technique has been implemented to systematically modify elevations and Manning's coefficients to evaluate the consequence of errors in determining these parameters. Initial evaluations indicated cross-section spacing significantly effects computational results.