What is a living systematic review? We define an LSR as a systematic review which is continually updated, incorporating relevant new evidence as it becomes available. Practically, this means that LSRs: • Are underpinned by continual, active monitoring of the evidence (i.e. monthly searches) • Immediately include any new important evidence (meaning data, studies or information) that is identified • Are supported by up-to-date communication about the status of the review, and any new evidence being incorporated While core review methods are not fundamentally different to other Cochrane Reviews, an LSR should additionally include explicit, transparent and predefined decisions on: • How frequently new evidence is sought and screened • When and how new evidence is incorporated into the review Why living systematic reviews? Living systematic reviews (LSRs) provide a new approach to support the ongoing efforts of Cochrane and others to produce evidence that is both trustworthy and current. The concept of living evidence synthesis and related outputs, such as living guidelines, are of increasing interest to evidence producers, decision makers, guideline developers, funders and publishers, as a way to seamlessly connect evidence and practice. The possibility of a scaled-up living evidence approach has only recently been within reach, due to a number of technological and data-related innovations, such as online platforms, linked data, and machine learning. Concurrently, research groups are embracing larger collaborations, open and shared data, and the growth of the citizen science movement, opening up the possibility of communities with a common interest maintaining high value datasets and associated LSR. Living systematic review pilots Project Transform is currently piloting LSRs as part of the Production Models component with the following groups: • Cochrane Gynaecological, Neuro-oncology and Orphan Cancers • Cochrane Musculoskeletal • Cochrane Acute Respiratory Infections • Cochrane Heart An evaluation plan is in place, and the LSR guidance will be revised on the basis of the evaluation once the pilots are completed. The expected timeline for this is mid-2018.