BACKGROUND: When considering whether a patient is fit for surgery, a comprehensive patient assessment represents the first step for an anaesthetist to evaluate the risks associated with the procedure and the patient's underlying diseases, and to optimise (whenever possible) the perioperative surgical journey. These guidelines from the European Society of Anaesthesiology and Intensive Care Medicine (ESAIC) update previous guidelines to provide new evidence on existing and emerging topics that consider the different aspects of the patient's surgical path. DESIGN: A comprehensive literature review focused on organisation, clinical facets, optimisation and planning. The methodological quality of the studies included was evaluated using the GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) methodology. A Delphi process agreed on the wording of recommendations, and clinical practice statements (CPS) supported by minimal evidence. A draft version of the guidelines was published on the ESAIC website for 4 weeks, and the link was distributed to all ESAIC members, both individual and national, encompassing most European national anaesthesia societies. Feedback was gathered and incorporated into the guidelines accordingly. Following the finalisation of the draft, the Guidelines Committee and ESAIC Board officially approved the guidelines. RESULTS: In the first phase of the guidelines update, 17 668 titles were initially identified. After removing duplicates and restricting the search period from 1 January 2018 to 3 May 2023, the number of titles was reduced to 16 774, which were then screened, yielding 414 abstracts. Among these, 267 relevant abstracts were identified from which 204 appropriate titles were selected for a comprehensive GRADE analysis. Additionally, the study considered 4 reviews, 16 meta-analyses, 9 previously published guidelines, 58 prospective cohort studies and 83 retrospective studies. The guideline provides 55 evidence-based recommendations that were voted on by a Delphi process, reaching a solid consensus (>90% agreement). DISCUSSION: This update of the previous guidelines has covered new organisational and clinical aspects of the preoperative anaesthesia assessment to provide a more objective evaluation of patients with a high risk of postoperative complications requiring intensive care. Telemedicine and more predictive preoperative scores and biomarkers should guide the anaesthetist in selecting the appropriate preoperative blood tests, x-rays, and so forth for each patient, allowing the anaesthetist to assess the risks and suggest the most appropriate anaesthetic plan. CONCLUSION: Each patient should have a tailored assessment of their fitness to undergo procedures requiring the involvement of an anaesthetist. The anaesthetist's role is essential in this phase to obtain a broad vision of the patient's clinical conditions, to coordinate care and to help the patient reach an informed decision.