Tehran University of Medical Sciences Iranian Journal of Public Health 2251-6085 39 1 2010 03 15 64 69 S Prinja 2015 10 03 Policy making in health is largely thought to be driven by three ‘I's namely ideas, interests and institutions. Recent years have seen a shift in approach with increasing reliance being placed on role of evidence for policy making. The present arti­cle ascertains the role of ideas and ideologies in shaping evidence which is used to aid in policy decisions. The article dis­cusses different theories of research-policy interface and the relative freedom of research-based evidence from the influence of ideas. Examples from developed and developed countries are cited to illustrate the contentions made. The article high­lights the complexity of the process of evidence-based policy making, in a world driven by existing political, social and cul­tural ideologies. Consideration of this knowledge is paramount where more efforts are being made to bridge the gap be­tween the ‘two worlds' of researchers and policy makers to make evidence-based policy as also for policy analysts. https://ijph.tums.ac.ir/index.php/ijph/article/view/3135 https://ijph.tums.ac.ir/index.php/ijph/article/download/3135/2934