The role of economic analysis is not only to estimate the economic consequences of preventive programmes, their costs and benefits, but also to contribute to an understanding of individual and collective choice in allocating resources to prevention. A basic economic concept of relevance for prevention is investment. For investments, costs will always precede benefits in time. This means that the choice of discount rate is of great importance for the value of prevention. The identification and evaluation of costs for preventive programmes has its special problems. The 'opportunity cost' of time is important, both for a correct estimation of the social costs of preventive programmes and for an understanding of individual behaviour in relation to prevention. 'Willingness to pay' is the basic concept in the economic evaluation of benefits from prevention. The use of this concept in health care has been criticized, but it is preferable to indirect methods of benefit evaluation. However, for many preventive programmes, it is sufficient to study cost-effectiveness. The distributional consequences of different measures of effectiveness have to be recognized, as well as the role of prevention in reducing inequalities in health in general.