OBJECTIVES: Any economic evaluation of a health care intervention is only as good as the effectiveness data it is built upon (Drummond 1997). Despite this knowledge, the quality of information on clinical effectiveness is still poor. The main reason is that most data, at least on medicinal drugs, is tailored towards obtaining a market authorisation. Competent authorities, in the European Union, the United States and Canada, are often granting market access on the basis of efficacy data alone. Because of this lack of effectiveness data, information is mostly extrapolated from the existing efficacy data. In theory it should be left to evidence-based-medicine specialists to estimate this information. In practise this is done as an integral part of most economic evaluations. We challenge this practise and propose to separate the estimation of effectiveness from the overall process of economic evaluations. Our main argument is that the estimation of effectiveness is not necessarily a core competency for authors of economic evaluations. Hence this crucial issue gets too little attention in discussions and guidelines of economic evaluations. Subsequently we argue that this niche of evidence-based-medicine is still underdeveloped. It urgently needs scientific discussion and development of its own guidelines. We propose that the estimation of effectiveness on the basis of efficacy data should be done as an endeavour in itself. This would make the appraisal of these two distinct procedures, namely effectiveness assessment and economic evaluation, clearer and thus more valuable. The European Union is currently trying to develop this field (Pharmaceutical Forum Conclusions – Press release 09/29/2006).