The feasibility of using electrical communication between wells to determine the average interwell fluid saturation was tested with a long core and three-dimensional model reservoirs. Two methods were proposed. The first employed an oxidizing solution in one well and a reducing solution in another to obtain an electric current through the reservoir from chemical reaction; the second, an impressed current between the wells and measurement of the potential difference. Experimental determination of the overall brine saturation using the electrical fields agreed with the volumetric amounts of brine and oil with which the model reservoirs were saturated. General mapping of the saturation distribution of the three-dimensional reservoir was also possible using a finite-difference solution of Poisson's equation.