The three chapters in Part IV focus upon the methods and methodologies employed by work and organizational psychologists to understand, describe, and intervene in organizational change processes. Given the contributions already made by management scientists generally, and by organization development specialists and strategic management practitioners in particular, it is instructive to ask what organizational psychology might add. What methods are available to organizational psychologists? What are their merits and demerits? In which circumstances are certain methods more appropriate than others? With what criteria do we make judgements about our research methods and interventions? And ultimately, how are we to decide whether our methods generate accurate and comprehensive accounts of the multi-faceted phenomena of organizational change? Underlying this last question are the ubiquitous issues of the epistemological and ontological bases of our efforts to research into processes of organizational change. The three chapters in Part IV address these issues, but in quite differing ways.