This paper reports the use of a qualitative methodology for conducting longitudinal case study research on software development. We provide a detailed description and explanation of appropriate methods of qualitative data collection and analysis that can be utilized by other researchers in the software engineering field. Our aim is to illustrate the utility of longitudinal case study research, as a complement to existing methodologies for studying software development, so as to enable the community to develop a fuller and richer understanding of this complex, multi-dimensional phenomenon. We discuss the insights gained and lessons learned from applying a longitudinal qualitative approach to an empirical case study of a software development project in a large multinational organization. We evaluate the methodology used to emphasize its strengths and to address the criticisms traditionally made of qualitative research.