An approach to risk analysis developed for BP International in the late 1970's based upon a range of earlier North American studies is outlined. Experience with its use for some twenty major projects to date is discussed. Key issues are summarized and briefly related to experience with subsequent studies of quite different problems in Canada and the U.S.A. The emphasis is on the way models are structured, the effect of model structure on parameter estimation, the impact of methods on model structuring, and the importance of the role played by risk analysts in relation to project planners and management