Uncertainty for policy makers is not new but the pressure to make decisions under conditions of uncertainty is perhaps greater than ever. The arrival of new scientific developments such as pharmacogenetics offers potentially great benefits . They have passionate supporters as well as doubters. The evidence is often extensive but unclear and policy makers may find themselves under pressure to make decisions before they feel that the evidence is compelling.The UK is particularly well placed to play a leading role in (...) the development of pharmacogenetics and is equally well placed to derive the benefits to both health and wealth that could flow from this. However, the uncertainties threaten to overwhelm the capacity of policy makers to act effectively. The uncertainties are both about the context within which the science and delivery of pharmacogentics is being developed and about the interests that could be served. This paper maps these uncertainties and concludes with some suggestions, drawing on deliberative democracy and futures thinking, as to how policy makers might manage the tensions and dilemmas they face by moving from an unstable, emergent policy arena to a more stable one. (shrink)