In this paper, we investigate and test the assumptions of outpatient healthcare appointments scheduling. There is significant interest in appointment scheduling in both healthcare practice and among scholarly researchers, but there has been little systematic comparison of practice versus theory. Using mathematical models and empirical surveys of clinic practitioners, we quantitatively and qualitatively evaluate the assumptions frequently made in the domain of outpatient healthcare appointment scheduling literature. Between theory and practice, we compare and contrast objective functions, relevant costs and benefits, appointment scheduling methods, prevalence and handling of no-show patients, schedule construction, and open access scheduling.