Balance velocities for the Greenland ice sheet have been calculated from a new digital elevation model, accumulation rates compilation and an existing ice thickness grid, using a fully two-dimensional finite difference scheme. The pattern of velocities over the ice sheet is presented and compared with velocities derived from synthetic aperture radar interferometry for part of northern Greenland and a limited number of GPS data. This comparison indicated that the balance velocity scheme and boundary conditions used here provide a remarkably good represantation of the dynamics of the ice sheet inland from the margins. It is suggested, therefore, that these balance velocity data could provide a valuable method of constraining a numerical ice sheet model. The balance velocities were compared with the diagnostic velocity field calculated from several different configurations of a numerical ice sheet model. The general pattern of flow agrees well. the detail, however, is quite different. For example, the large (greater than 300 km) ice stream in the north east is not generated by the numerical model and much of the detailed flow pattern is completely lost due to the limited model resolution and limitations in the model physics.