This article presents the research findings of a study on task complexity and information-seeking activities in real-life work tasks. The focus was on perceived task complexity, which was determined according to the task performers' prior knowledge about the task ahead. This view on task complexity is closely related to research considering task uncertainty and analyzability. Information-seeking activities considered were a need to acquire different types of information and the subsequent use of different types of sources. The research data were mainly collected by (1) self-recorded journals that were filled out by municipal administrators in the course of performing their ordinary work duties (altogether 78 task diaries), and (2) subsequent interviews. The results indicated that there is a relatively strong relationship between types of information and types of sources. The effects of task complexity made experts more attractive as a source than other people and all types of documentary sources.