Effective management of uncertainties and life-cycle risks is critical to the success of oil and gas projects and is, in fact, the central challenge of the E&P business. This seminar has been designed to allow SPE members to share examples and anecdotal experience of making decisions under high subsurface and surface uncertainty and risk associated. It will summarise the interaction between different elements affecting critical decisions in the oil and gas industry and clarify the distinctions between technical and organisational complexity when choosing between different development options. There will be a review of high stake decisions in organisationally complex settings, from drilling through to reservoir modelling up to economics