See Maass and Shine (doi:10.1093/brain/awz121) for a scientific commentary on this article. Entorhinal cortex is affected early in Alzheimer’s disease and is critical for navigation. Using immersive virtual reality, Howett et al. reveal navigational deficits in biomarker-positive patients with mild cognitive impairment. Navigational deficits are more sensitive and specific to Alzheimer’s disease risk than a battery of reference cognitive tests.