During the past several years, the Global Energy and Water-Cycle Experiment (GEWEX) Continental Scale Experiments (CSEs) began to develop the “best available” description of global and regional atmospheric and land water and energy budgets. Since few regional or global hydroclimatological observations were available when these water and energy budget studies began, initial studies mainly included global and regional atmospheric analyses along with macroscale hydrologic models. Although the analysis systems are still highly model dependent, at least there are many more observational constraints than free running general circulation models. However, a number of observationally based data sets have finally become available, including: the Global Precipitation Climatology Project (GPCP) precipitation, International Satellite Climate Comparison Project (ISCCP) radiation, and the Global Runoff Data Center (GRDC) runoff. We have therefore begun to compare the National Centers for Environmental Prediction / National Center for Atmospheric Research (NCEP/NCAR), NCEP / Dept. of Energy (DOE), and European Centre for Medium Range Forecasts (ERA40) reanalyses to these GEWEX sponsored observations. As will be shown the extra budget terms caused by the analysis constraints on the imperfect reanalysis models are not small. However, individual process errors in these models, which tend to cancel, are likely much larger. For example, analysis precipitation errors are likely balanced mainly by evaporation errors; however, errors in other hydrometeorological processes, such as regional runoff and moisture convergence, are almost as large, especially for certain regions, such as the Amazon and GAME tropics. An assessment of the possible global and regional water and energy budget errors in the reanalyses will be presented at the meeting.