This paper presents a technique for monitoring CO2-flood response and performance with wireline-derived petrophysical data. Gas saturation data derived with this method are in agreement with independent estimates available from a CO2 pilot project. Examples show the application of the method in the Denver unit (DU). Results obtained with this technique are useful for quantifying CO2 saturation, monitoring flood progress and vertical sweep, identifying potential out-of-zone injectant losses, and detecting nonresponding layers.