The spatial and temporal variation of electrical conductivity in saturated sands during steam injection has been measured and modeled. Experiments consisted of introducing steam into one end of a tube filled with sand saturated with a slightly saline solution. A steam condensation front formed, separating the mixed-phase steam zone from the liquid zone. Measurements of electrical conductivity were made at 10 locations along the tube using a four-electrode technique. Results show that conductivity starts at a constant value, decreases before the steam front arrives and then, immediately prior to the steam front arrival, goes through a maximum before dropping by a factor of about 25. These variations can be explained by, first, a dilution of the interstitial solution causing the initial drop in conductivity; second, an increase in temperature of the solution immediately prior to the arrival of the steam front causing the conductivity maximum; and, finally, the large drop in conductivity due to the combined effects of a decrease in saturation and dilution of the residual liquid in the two-phase zone. Mathematical solutions of a set of differential equations that take into considertion all of these effects are presented. These solutions reproduce the significant features of the conductivity data. This study suggests that the measurement of changes in the subsurface conductivity field during steam injection operations may indicate the location of ionic concentration, temperature, and steam saturation fields. ¿ American Geophysical Union 1993