A series of studies is presented in which an electrical-impedance tomography (EIT) system is validated for two-phase flow measurements. The EIT system, developed at Sandia National Laboratories, is described along with the computer algorithm used for reconstructing phase volume fraction profiles. The algorithm is first tested using numerical data and experimental phantom measurements, with good results. The EIT system is then applied to solid-liquid and gas-liquid flows, and radial phase volume fraction profiles within a circular cross-section are determined. These profiles are compared to results from an established gamma-densitometry tomography (GDT) system. In the solid-liquid flows, the average solid volume fractions measured by EIT are in good agreement with nominal values. In the gas-liquid flows, average gas volume fractions and radial gas volume fraction profiles from GDT and EIT are also in good agreement.