The Second Global Soil Wetness Project (GSWP2) is a land-surface modeling activity of the Global Land-Atmosphere System Study (GLASS) and the International Satellite Land-Surface Climatology Project (ISLSCP), both contributing projects of the Global Energy and Water Cycle Experiment (GEWEX). The first phase of GSWP2, a global 10-year multi-model simulation and comparison using the ISLSCP Initiative II data set (1986-1995), begins later this year. In addition to providing a large-scale test-bed for comparison of land surface schemes (LSSs), several sub-projects are proposed. Estimates of continental and global-scale surface energy and water budgets will be calculated, and inter-model uncertainties will be established. The ability of multiple LSSs to simulate large-scale interannual variations will be investigated. GSWP2 will serve as a global platform for the application of remote sensing to LSS calibration, validation and assimilation. Sensitivity of simulated fluxes and state variables to uncertainties in atmospheric forcings, soil, and vegetation parameters will be examined. The ability of simple and intermediate models to replicate the behavior of complex LSSs will be explored, as a tool for better understanding of surface processes. In situ validation of LSSs with data from numerous field campaigns conducted during the 10-year period will also be possible. GSWP2 will also explore promising new data management technologies, including the capability to perform model integration and analysis with distributed data sets, reducing the data management burden on participants. A subsequent continental phase will focus on North America, and will also investigate issues of aggregation (from 1/8 degree to 1 degree).