This article serves as the introduction to the Special Section called “Toward Implementing Physiological Measures in Clinical Assessments of Adult Mental Health.” As such, it provides an overview of the importance of integrating assessments of physiological and subjective processes in mental health assessments and discusses the Research Domain Criteria (RDoC) initiative. In addition, it summarizes the findings from the four empirical studies published in the Special Section. Collectively, these studies sought to illustrate how physiological assessments can be incorporated in mental health assessments conducted in applied research and clinic settings. In all, we hope that this Special Section will inspire the type of interdisciplinary research spanning basic and applied work that will be critical to advancing the RDoC initiative.