Three-phase oil/water and gas/water experiments were performed to investigate the dependence of relative permeability on wettability. Quantitative fluid saturations were determined with an X-ray computer-aided tomography (CT) scanner. Oil, water, and gas distributions generated in 3D were found, in some cases, to be highly nonuniform and dependent on experimental conditions. Results indicate that some traditional thinking about measuring relative permeability may be in error and merits further investigation.