Coreflood experiments in naturally heterogeneous sandstone outcrop cores were conducted and simulated. Displacements included waterfloods and polymer floods containing tracers for oil or water during single-phase and two-phase flows. Displacements of viscous polymer solution were unstable. The cores were characterized by air permeability measurements on each square centimeter of each face and by computerized tomography (CT) scans of core cross sections spaced I cm apart along the core length. Characterization data were used for fine-grid simulations. The agreement between the experiments and simulations is good. Simulations with coarser-grid physical descriptions then were made by use of effective properties.