Epidemiology is the method of choice for quantifying and interpreting health phenomena, placing them into perspective to allow trend analysis and projections. It is a tool for analysis, evaluation and forecasting and is thus indispensable in the decision-making process. However, this comprehensive technique has its limitations since health is the result of complex interactions: individual requirements do not always correspond to the overall needs of the community; consideration has to be given to solidarity and the necessity for cost-sharing; and the decision process is strongly influenced by social, cultural, religious and political factors which defy quantification and, on occasion, any rational course of action. Each indicator only takes into account one aspect of the situation and the pertinent indicator should therefore be carefully selected. At the same time, any choice implicitly signifies value judgements-often unnoticed-which need to be balanced and validated in relation to the ethical values of the community in order to be of any assistance to decision-making. Decision-making is a qualitative political process which, although based on the quantitative analysis supplied by epidemiology, cannot be limited to it. Each approach enhance the other, but they should not be confused if freedom to act is to be preserved from being locked into some kind of mechanical process that is unacceptable both to man and to society.