It is generally rare to find archaeological sites in the Southwest that retain the type of contextual integrity that the Sierra Diablo Cave exhibits. Often times, cave sites such as the one currently studied offer excellent preservation of cultural materials due to the general lack of moisture and isolation from wind and water erosion. The research aimed to determine when the site was occupied as well as the types of activities that were occurring during those occupations. It exhibits an extensive stratigraphic sequence that contains a well pronounced Late Archaic Period assemblage (Strata A and B) and a Late Pleistocene/Early Holocene deposit in a lower stratum (F), at minimum. Paleoindian sites with intact cultural deposits are critical to our understanding of Late Pleistocene archaeology because they are uncommon. Subsurface investigations consisted of four excavation units and two trenches, sampling 17 1.0-m by 1.0-m excavation squares. Because of the variety and frequency of cultural materials in undisturbed contexts, this study shows that the site exhibits great potential in its ability to contribute to our understanding of the Late Archaic and Paleoindian periods of the prehistoric Trans-Pecos region of Texas.