Project Portfolio Management (PPM) is an area of organisational activity that attempts to govern the selection and of management of an organisation's ICT projects. As a domain of study PPM is characterised by undisciplined diverse opinion as to its nature and a commercial approach to management standards, business literature and software support. In this paper we examine the use of the State-Transition Approach as a possible means for bringing structure to the study of the PPM domain. We demonstrate its effective use for the analysis of the literature, research question formulation, research design and data collection and analysis. We argue that PPM is an example of a class of problematic, complex phenomena of interest to the IS discipline and that an adaptation of the state-transition approach seems to offer a useful conceptual framework for research across that class.