Effective management of acid-base disorders depends on accurate diagnosis. Three distinct approaches are currently used in assessing acid-base disorders: the physiological approach, the base-excess approach, and the physicochemical approach. There are considerable differences among the three approaches. In this review, we first describe the conceptual framework of each approach, and comment on its attributes and drawbacks. We then highlight the application of each approach to patient care. We conclude with a brief synthesis and our recommendations for choosing an approach.