In a previous study we found that volume variability during an El Ni¿o--Southern Oscillation (ENSO) event is well described by variations in, and redistribution of, the heat content for any given region within the tropical Pacific. In this study we use numerical model temperature and velocity fields in a Lagrangian analysis of heat content variability. These three-dimensional fields are used to examine specific warm and cool anomaly regions by computing trajectories back through time to the origins of the anomalously warm or cool water. In particular, we find that three distinct pathways are important in creating and maintaining the warm eastern equatorial anomaly, including pathways in the basin interior in both hemispheres. After this warm anomaly at peak ENSO, off-equatorial anomalies form both in the eastern Pacific and in the far western Pacific. The west Pacific off-equatorial cool anomalies are attributed to ENSO variations in the Ekman pumping in those regions.