In response to the need for more sustainable business practices, this paper presents an approach to decision support based on the idea of "critical systems engineering". This requires, among others, the involvement of a potentially diverse array of stakeholders in interactive decision processes, the explicit consideration of all types of uncertainties, and the complementary, and informed, use of methodologies from several disciplines. The approach is based on multiple criteria decision analysis (MCDA), but extends this by incorporating an integrated approach for the consideration of different types of uncertainties. The approach and associated tools are illustrated for two technology selection decisions associated with electrical power generation. Using the concept of "decision spaces", it is possible to show the relationship between these power generation decision contexts and more general decision making associated with process design. (c) 2006 Elsevier Ltd. All rights reserved.