Lecanemab is an anti-amyloid monoclonal antibody, recently approved in the UK as a treatment for mild cognitive impairment (MCI) and mild dementia due to Alzheimer's disease (AD) in adults who are apolipoprotein E ε4 gene (APOE4) heterozygotes or non-carriers.A group of UK neurologists, old age psychiatrists and geriatricians with expertise in AD convened to agree appropriate use recommendations for lecanemab in UK clinical practice. The primary focus of these recommendations is safety.Eligibility criteria for lecanemab in the UK include (a) a clinical diagnosis of MCI or mild dementia due to AD, (b) the presence of amyloid-β pathology, confirmed using approved methods (ie, an amyloid positron emission tomography scan or cerebrospinal fluid assay) and (c) APOE4 heterozygous or non-carrier status. Eligibility screening should be conducted in secondary care and those identified as being potentially eligible for lecanemab should be referred to a specialist centre for confirmation of the likely pathological diagnosis, APOE4 counselling and testing and a multidisciplinary consensus decision regarding treatment eligibility. Lecanemab is administered as an intravenous infusion every 2 weeks, and those eligible for treatment should have brain magnetic resonance imaging (MRI) scans prior to the 1st, 5th, 7th and 14th infusions. Specific guidance is provided for safety monitoring and management of potential adverse reactions, including amyloid-related imaging abnormalities and infusion-related reactions.The introduction of lecanemab into UK clinical practice provides an important opportunity to improve services for all people living with dementia, not just those eligible for lecanemab treatment.