A new empirical model has been developed to estimate three-phase relative permeability. A literature review indicates that use of a model based on saturation-weighted interpolation of two-phase relative permeabilities provides more accurate data. Saturation-weighted interpolation is extended to account for oil and gas trapping and allow oil-layer drainage. Compositional consistency is introduced to account for miscible and near-miscible flows. From a single set of two-phase oil/water, gas/water, and gas/oil measurements, three-phase relative permeabilities can be predicted for any saturation path, reservoir wettability, and hydrocarbon composition.