Alzheimer's disease was identified almost a century ago. Cognitive morbidity (deterioration in memory, attention, language, and executive functioning) was regarded as a sufficient index for the description and diagnosis of Alzheimer's disease. Within the cognitive discourse, the importance of neuropsychiatric and neurobehavioural referents was often eschewed. Recent research studies attest to the profound impact of the non-cognitive symptoms on the quality of life of both patient and caregiver. The purpose of this article is to review studies on psychosis in Alzheimer's disease, examine its prevalence, and discuss its manifestation with reference to the association between neuropathology and psychotic disturbances. The importance of clarifying the validity of the construct 'psychosis in Alzheimer's disease', the specificity of symptoms, and the phenomenology of subtypes with their distinct clinical and biological associations is addressed.