There is a need for large trials that test the clinical effectiveness of interventions in the field of perioperative medicine. Clinical outcome measures used in such trials must be robust, clearly defined and patient-relevant. Our objective was to develop standards for the use of clinical outcome measures to strengthen the methodological quality of perioperative medicine research. A literature search was conducted using PubMed and opinion leaders worldwide were invited to nominate papers that they believed the group should consider. The full texts of relevant articles were reviewed by the taskforce members and then discussed to reach a consensus on the required standards. The report was then circulated to opinion leaders for comment and review. This report describes definitions for 22 individual adverse events with a system of severity grading for each. In addition, four composite outcome measures were identified, which were designed to evaluate postoperative outcomes. The group also agreed on standards for four outcome measures for the evaluation of healthcare resource use and quality of life. Guidance for use of these outcome measures is provided, with particular emphasis on appropriate duration of follow-up. This report provides clearly defined and patient-relevant outcome measures for large clinical trials in perioperative medicine. These outcome measures may also be of use in clinical audit. This report is intended to complement and not replace other related work to improve assessment of clinical outcomes following specific surgical procedures.