For more than a century, soil respiration measurements have been used to understand soil microbial activity in different ecosystems and contexts. Continued methodological development and advances in sensing technologies are opening new avenues for exploration and insight. Nonetheless, the underlying mechanisms of many of these measurements continue to be debated. This chapter reviews commonly used respiration-based methods for assessing soil microbial characteristics, including the historical context and biological bases of different applications in laboratory and field settings. Along with this history, it address some of the most critical challenges and uncertainties related to respiration-based measurements, and provides a case study showing how different respiration tests were used to assess how cover cropping, tillage, and fertility management practices affect soil microbial functioning in two agricultural fields in Virginia, U.S. The chapter concludes by discussing future needs and trends in soil respiration research and by providing resources for further information.