Dr. William Halliday, medical surgeon and karst terrain authority, relates segments of his life story back to the development of his interest in karst and caving. Dr. Halliday recounts his involvement as a charter member of the Medical Section of the National Speleological Society (NSS), founding several grottos, and the political activism in which he participated on their behalf. He describes a few of his international caving adventures, the difference between karst and pseudokarst, and his impressions on whether there exists an attitudinal divide between geologists and amateur sport cavers. The interview ends with Dr. Halliday’s personal belief that Mars exploration should be pivotal in the future of karst research. Interview conducted July 23, 2007 at the National Speleological Society convention in Marengo, Indiana.