The common denominator of a growing number of hard decisions facing modern societies is the need to determine 'how safe is safe enough?'. The authors begin by defining acceptable-risk problems and analysing why they are so difficult to resolve, considering such issues as uncertainty about their definition, lack of relevant facts, conflicting and conflicted social values, and disagreements between technical experts and the lay public. Drawing on their own experience in risk management as well as the relevant research literatures, they identify and characterise the variety of methods that have been proposed for resolving acceptable-risk problems. They subject these methods to a rigorous critique in terms of philosophical presuppositions, technical feasibility, political acceptability, and validity of underlying assumptions about human behaviour. The authors construct a framework for deciding how to make decisions about risks, and offer recommendations for research, public policy, and...