We have mapped the catchment region of Pine Island Glacier, Antarctica, using ERS-1 and ERS-2 radar altimetry and synthetic aperture radar (SAR) interferometry. The radar altimeter data were converted to a digital elevation model (DEM), using an algorithm we developed that corrects for slopes and grids the surface elevation estimates in a single step. We used the DEM and precise (postprocessed) orbital ephemerides to generate terrain-corrected and geolocated complex radar imagery. Interferometric pairs on both ascending and descending orbits, corrected by means of the DEM, yielded components of ice surface motion in the radar look direction. Where possible, we combined velocity components from ascending and descending tracks to produce vector velocities; elsewhere, the velocity was calculated by assuming the direction of motion is down the surface slope. The velocity map reveals a system of tributaries that channel ice from the basin-like catchment area into the fast flowing downstream trunk of Pine Island Glacier. None of the tributaries shows a clear onset region. Instead, the ice speed gradually increases, along with a gradual decrease in driving stress, along each tributary. We combined the velocity data with sparse information on ice thicknesses and snow accumulation rates to calculate an approximate mass balance. We find that the region is in balance within an uncertainty of ∼30% of the total mass throughput.