Plant safety and reliability analysis is a complex task often with a need for computer support. The phases of the analysis are information collection, qualitative hazard identification, system modelling and analysis, and consequence assessment. Computer software tools have been developed for different analysis tasks. They are very useful in the automation of the routine parts of the analysis. However, knowledge-based techniques are needed in the development of more powerful tools. This paper gives a short review of software tools developed for the documentation and calculation tasks of safety and reliability analysis. The main emphasis is on describing and evaluating the possibilities of knowledge engineering to support human reasoning in hazard identification and system modelling. An example of an advanced software environment, stars, for carrying out multi-level knowledge-based safety and reliability analysis is presented.