A main concern of process-oriented knowledge management (pKM) is the creation of an environment that enhances the productivity of knowledge work while maintaining a strong link to the creation of customer value in business processes. Knowledge work is creative work targeted at the creation of new knowledge. Enterprise knowledge infrastructures represent an important means in this context as they offer integrated knowledge services for discovery and publication of knowledge, for communication and for learning. However, process-oriented KM currently lacks ways for a systematic integration of knowledge work, business processes and knowledge services. The general goal of this dissertation is the development of such an approach. The concept of knowledge work situation is proposed that describes a recurring situation where a knowledge worker can, should or must switch from a business-oriented function to a knowledge action. It is specified by the context of the situation and triggered by occasions to learn and to generate knowledge related to organizational core competencies. This work includes a detailed review and comparison of modelling approaches proposed in pKM, which informs the concept proposed. On the level of systems, a process-oriented perspective on enterprise knowledge infrastructures is developed and possibilities for situation-oriented, flexible support of knowledge work are presented. This work includes an empirical exploration of the knowledge work situation concept. Therefore, 31 semi-structured interviews have been conducted, transcribed and structured with the help of a qualitative content analysis approach. The results have been used in order to reflect on and to revise the concept developed. Overall, this work contributes to pKM by offering an innovative, theoretically well-founded and empirically grounded concept for the description of knowledge work in business processes.