This review was carried out with the aim of updating an existing systematic review conducted by the University of York in 2008. It examined the impact of ‘opt-out’ legislation on organ donation rates. This paper presents three main strands of evidence: International evidence suggests that an association exists between presumed consent legislation and increased organ donation rates; Recent surveys indicate that there is significant support for the introduction of an opt-out system for organ donation in Wales; Experimental literature provides evidence for a mechanism through which presumed consent might increase organ donation, through the influence of the default position.