This chapter provides an overview for performing and interpreting electron paramagnetic resonance (EPR) measurements on spin-labeled proteins. It focuses on site-directed spin labeling (SDSL) methods as appropriate for monitoring dynamics and conformational changes in membrane proteins. The chapter provides recent examples that illustrate the various SDSL-EPR techniques for revealing the connection between structure and mechanism for membrane pumps, channels, and transporters. The examples include the use of SDSL-EPR strategies for studying gating mechanisms, substrate and drug binding, and overall dynamics and structural arrangement of membrane transporters and channels accompanying their function. The chapter presents other recent reviews on SDSL in membrane proteins and other protein systems, as well as recent reviews on technological advances in methodology, instrumentation, and data analysis. It concludes with a discussion on some current challenges of SDSL for membrane proteins and the strategies under development to address these challenges.