This paper describes the findings of a systematic literature review that was undertaken to inform the third edition of the Intensive Care Society's (ICS) Guidelines for the Transport of the Critically Ill Adult, which has recently been published. Thirty-eight articles were identified relating to the process of adult patient transfer. The bulk of the articles related to transfer quality, including review articles and audits assessing both the standard of transfers and compliance with relevant guidelines. The review demonstrates that the quality of transfers remains a concern, but much of the data is from single centre audits and case series, which are thought to provide the weakest level of evidence. The guidelines have been extensively updated to reflect both current practice and emerging evidence, but it is clear that measures are still needed to improve the quality of transfers.