This thesis deals with the problems of designing display systems for process plants. We state the reasons why it is important to discuss information systems for operators in a control room, es-pecially in view of the enormous amount of information available in computer-based supervision systems. The state of the art is discussed: How are supervision systems designed today and why? Which strategies are used? What kind of research is going on? Four different plants and their display systems, designed by the author, are described and discussed. Next we outline different methods for eliciting knowledge of a plant, particularly the risks, which is necessary information for the display designer. A chap-ter presents an overview of the various types of operation refer-ences: constitutive equations, set points, design parameters, com-ponent characteristics etc., and their validity in different situa-tions. On the basis of her experience with the design of display systems; with risk analysis methods and from 8 years, as an engi-neer-on-shift at a research reactor, the author developed a method to elicit necessary information to the operator. The method, a combination of a Goal-Tree and a Fault-Tree, is described in some detail. Finally we address the problem of where to put the dot and the lines: when all information is ‘on the table’, how should it be presented most adequately. Included, as an appendix is a paper concerning the analysis of maintenance reports and visualization of their information. The purpose was to develop a software tool for maintenance supervision of components in a nuclear power plant.