Several important processes involve the flow of three immiscible fluids through porous media, such as the fl?ow of oil, water and gas in petroleum reservoirs, or water, nonaqueous-phase liquid and air in underground aquifers. Multiphase flow functions (relative permeability and capillary pressure) are important to simulate the flow in such systems. Unfortunately, there are few, if any, reliable estimates of these flow properties from laboratory experiments. One of the main reasons for this is the use of unsupported simplifications in the procedures for determining property estimates from measured data. We present a method for simultaneous estimation of three-phase relative permeability and capillary pressure functions from laboratory experiments. The method is not limited by restrictions in the experimental design or assumptions regarding the saturation dependence or shape of the functions to be estimated. The method is demonstrated with simulated experiments. It is shown that with a suitable experimental design, regions of the functions represented by the measured data can be determined accurately.