The new economy, which has emerged in the last two decades, is critically dependent on the capacity to generate, process and efficiently apply knowledge. Yet, with notable exceptions, knowledge work has not been seriously addressed in the literature. The purpose of this paper is to understand the internal characteristics of knowledge work. Our analysis is concerned with the concept and nature of knowledge work rather than the philosophical questions that underlie it. We interpret knowledge work is as work that is based on a body of knowledge, usually entails working on representations of the objects of work, stipulates typically a deep understanding of the objects of work, and the outputs of which entail knowledge as its essential ingredient. These elements are used in characterise knowledge work. The paper also discusses how this analysis contributes to the development of a theoretical model of knowledge work