This article is part of a series written for people responsible for making decisions about health policies and programmes and for those who support these decision makers. Evidence about local conditions is evidence that is available from the specific setting(s) in which a decision or action on a policy or programme option will be taken. Such evidence is always needed, together with other forms of evidence, in order to inform decisions about options. Global evidence is the best starting point for judgements about effects, factors that modify those effects, and insights into ways to approach and address problems.