Studies of plethodontid physiology were quite common in the 1960s, 1970s, and into the early part of the 1980s. Since this time, studies of other aspects of plethodontid biology flourished, while physiological studies lagged behind. Organismal physiology is enjoying a resurgence of interest as researchers attempt to understand threats to biodiversity. In this paper, I outline our current understanding of plethodontid physiology, focusing primarily on energetics, water loss, and endocrine physiology and close by suggesting several avenues for future research. Although we have a good understanding of metabolic physiology in plethodontids, we have considerably fewer data concerning other aspects of plethodontid physiology. I urge researchers to revisit hypotheses and patterns suggested by early studies and expand the breadth of inquiry to multiple levels of ecological organization (individual, population, and species levels). Finally, there is a paucity of data concerning spatial and temporal patterns of physiological variation. Baseline data such as these are critical for formulating and testing broader hypotheses and for developing biologically grounded predictions of responses to anthropogenic stressors.