We reprocessed in time and depth two seismic lines from the Turtle Mountain area of Southern Alberta, Canada. Our objective was to improve the seismic imaging of the complex structures that form the mountain. Processing in the time domain was designed to attenuate noise and enhance signal in the data. The poststack and prestack time migrated sections are not adequately focussed and do not image correctly the structure deep in the section, which is expected to be relatively undeformed. Prestack depth migration provided better images. Our most effective velocity models for prestack depth processing were obtained by integrating all sources of geological and velocity information into the interpretation of seismic depth sections which were created through iterative updates of the velocity models. The depth processed sections show a more realistic geometry for the reflectors at depth than do the time sections and events are better focussed, making the sections easier to interpret than the time sections. Although the reprocessing improved the quality of the processed seismic data, we were not able to image the details of the shallow, steeply dipping strata of Turtle Mountain. In particular, the overturned beds are not imaged by the seismic data.