This paper proposes a typology of knowledge workers and their respective knowledge actions. The extant literature on the definition of knowledge work actions is examined and evaluated. The existing classifications of roles of knowledge workers are evaluated and extended with additional literature and empirical findings on the definition of a typology of knowledge worker roles. The empirical data in this paper comes from two studies. In the Task Execution Study 20, a knowledge worker had to carry out a selection of prepared tasks. The computer system that the participants were using was equipped with sensors, so that the execution steps of the tasks could be traced and analyzed. The data from the second study comes from a questionnaire survey of knowledge workers, which yielded 43 responses. The paper shows that the sampled users take on all identified knowledge worker roles, and that the knowledge work actions can be recognized in the sensor data from the first study. This paper contributes to the literature by proposing a new way of classifying the roles of knowledge workers and the knowledge actions they perform during their daily work. Furthermore, the paper provides a preliminary understanding of the relation between knowledge-intense work tasks, the roles they are executed in, and the tools that are used to accomplish the respective tasks. Copyright © 2011 John Wiley & Sons, Ltd.