In this chapter, we discuss the methodological challenges of applying a transactional perspective in the context of occupational therapy research. We suggest how a unit of analysis that focuses on where and when the transactions happen can be conceptualized and applied. Based on clinical practice and research on interventions in the home environment for older adults with functional limitations, we conclude that a transactional perspective contributes substantially to the understanding of how such interventions are integrated into everyday life. Further, we argue that the situation is an appropriate unit of analysis to grasp where and when the transactions happen. We present examples from two different empirical studies that employed the situation as the unit of analysis to illustrate key points of the argument. We end by discussing the challenges and strengths of using a non-traditional unit of analysis.