We report on variation in abundance of hibernating cave myotis (Myotis velifer) prior to the arrival of White-nose Syndrome. The report is based on cave surveys and literature reports in gypsum caves of western Oklahoma and the Texas panhandle. From 1988 to 2017, 34,625–195,234 M. velifer were estimated to occur in the hibernacula surveyed. This report provides important preexposure baseline data on population sizes in the region and will help researchers quantify the impact as the disease spreads into new environs. The population estimates will also serve as a data set for other research. Other species of bats encountered in the surveys were Townsend's big-eared bat (Corynorhinus townsendii), the tricolored bat (Perimyotis subflavus), and the big brown bat (Eptesicus fuscus). The changes in population sizes at the various hibernacula might be owing to a variety of factors, including annual variations in hibernacula microclimates, structural changes in hibernacula, changes in distribution patterns, ability of surveyors to locate and count bats, alterations of the surrounding habitats near hibernacula, or other unknown factors.