The Guadalupe Mountains provide dramatic exposures of the Capitan Limestone along the northwest margin of the Delaware Basin. These exposures provide unparalleled opportunities to examine lateral and vertical variations in the Capitan Limestone along a portion of the basin margin. Our work (Babcock, 1974, 1977; Yurewicz, 1976, 1977a) focused on outcrops of the massive facies of the Capitan Limestone in Slaughter, McKittrick, Walnut, and Dark canyons, and was supplemented by studies in Big, Rattlesnake, Bear, and Pine Springs canyons and Jurnigan Draw. These exposures show distinct, progressive changes in the Capitan as it prograded into the Delaware Basin. This paper summarizes those observations (Table 1). In order to document changes within the Capitan, we have divided it into three informal stratigraphic units: the lower, middle, and upper Capitan equivalent to the Seven Rivers, Yates, and Tansill formations on the shelf (Fig. 1). It is important to emphasize that our observations, although extensive, are not necessarily representative of the entire reef trend or even the entire exposed trend in the Guadalupe Mountains.