Mild Cognitive Impairment (MCI) is a diagnostic category indicating cognitive impairment which does not meet diagnostic criteria for dementia such as Alzheimer’s disease. There are public health concerns about Alzheimer’s disease (AD) prompting intervention strategies to respond to predictions about the impacts of ageing populations and cognitive decline. This relationship between MCI and AD rests on three interrelated principles, namely, that a relationship exists between AD and MCI, that MCI progresses to AD, and that there is a reliable system of (...) classification of MCI. However, there are also several ethical issues and problems arising in the AD/MCI relationship. These include early diagnosis and interventions, the effects on people with MCI, and the newer neuroimaging and neuropharmacological approaches used in diagnosis and treatment. All these issues pose questions about the principles of MCI in relation to AD, with implications for how MCI is understood, diagnosed, treated, and experienced by patients. This article analyses four challenging areas for neuroethics: the definition and diagnosis of MCI; MCI in relation to AD; clinical implications of MCI for ethical disclosure, diagnosis, and treatment; and the research implications of MCI. The significant connections between these areas are often overlooked, together with uncertainties overall. Patients, healthcare systems and society are best served by informed clinicians, academics and researchers. After 35 years, the store of MCI knowledge is expanding and evolving. (shrink)