Streamflow, which integrates the response of the land surface to atmospheric forcing over large areas, is a useful diagnostic to assess the performance of land surface schemes over large spatial scales. This paper uses observed runoff and streamflow data to assess the performance of the Canadian land surface parameterization scheme (CLASS), when operated within the Canadian Center for Climate modeling and analysis (CCCma) general circulation model (GCM) at 3.75¿ resolution, for three continental-scale river basins. Estimates of evapotranspiration obtained using atmospheric water balance, and soil moisture obtained using the VIC-2L model, are also used to assess the CLASS water balance simulations. Comparisons with observations of streamflow, and estimates of evapotranspiration and soil moisture, suggest that although CLASS simulates the annual cycle of evapotranspiration, streamflow, and soil moisture reasonably well, it overestimates evapotranspiration, underestimates runoff, and simulates slightly wetter soil moisture conditions. ¿ 2001 American Geophysical Union