BACKGROUND: Patient safety depends on nurses' clinical judgment. In post-anaesthetic care, objective scoring systems are commonly used to help nurses assess when a patient is ready to go back to the ward or be discharged home after day surgery. Although there are several criteria used to assess patient readiness for discharge from the post-anaesthetic care unit, evaluation of the validity and reliability of these criteria is scarce. AIMS: This article presents key findings from a systematic review conducted to identify the essential components of an effective and feasible scoring system to assess patients following surgical anaesthesia for discharge from the post-anaesthetic care unit. METHODS: The protocol for the systematic review of quantitative studies investigating assessment criteria for discharge of adult patients from the post-anaesthetic care unit was approved by the Joanna Briggs Institute and conducted consistent with the methodology of the Institute. Twelve databases and grey literature, such as conference proceedings, were searched for published studies between 1970 and 2010. Two reviewers independently assessed study eligibility for inclusion. Reference lists of included studies were appraised. RESULTS: Eight studies met the inclusion criteria; only one was a randomised controlled trial. Variables identified as essential when assessing a patient's readiness for discharge from the post-anaesthetic care unit were conscious state, blood pressure, nausea and vomiting, and pain. Assessment of psychomotor and cognitive recovery and other vital signs were also identified as relevant variables to consider. CONCLUSIONS: There was limited high-quality research regarding criteria to assess patient readiness for discharge from the post-anaesthetic unit. The key recommendations, with moderate to high risk of bias, include that assessment of specific variables (pain, conscious state, blood pressure, and nausea and vomiting) should be made before patient discharge. These key findings have informed a subsequent study to reach international consensus on effective assessment criteria and a project to test the clinical reliability of a tool for use by nurses in assessing patient readiness for discharge from post-anaesthetic care.