Abstract. The research presented in this paper investigates how observation of information- and communication-intensive work in hospital wards can be used to produce requirements for mobile clinical information systems. Over a number of years, we have explored how important properties of clinical situations can be captured through structured observations of actors, processes, and systems. In the paper, we present experience from four observational studies of a total of more than 400 hours in hospital wards. Based on the observational studies, we propose a framework for structured, tomographic, observation of clinical work practice. We also briefly discuss and illustrate how the field data can be analyzed and used as input to the requirements engineering process.