The objectives of contemporary medicine are basically to attenuate the consequences of chronic diseases and to improve the quality of life of the patient. All medical disciplines tend now to elicit therapeutic protocols directly from the general appreciation of the patients. The community is trying to obtain a transnosographic indicator which would allow the effects of its strategic choices between different areas of the health care system to be measured, taking into account the implications on the quality of life of the population. Individual preferences are now at the center of the decision-making process. Different experimental methods are being used to reveal them. Psychometricians use direct observation of a subject's reactions in a particular pathological situation: patients are asked to arrange the intensity of the impacts on bipolar numeric scales, but an actual metrical measure is not yet available. Traditionally, economists believe that in a market, only the consumer's choices enable us to estimate his level of satisfaction. In the health care field, where market mechanisms are not fully operational, they tend to extract the patients preferences through forced choices between hypothetical health states. A real metrical measure is thus obtained. The objective of this article is to exhibit these two methods: psychometric and economic, and to show how they have been implemented in French field research to obtain quality adjusted life years indicators: QALY's.