Memory dysfunction is the most notable feature of dementia of the Alzheimer type and is virtually mandatory for this diagnosis. The disruption of language ability is also a prominent clinical feature of this disease. Recent advances in cognitive neuropsychology suggest that Alzheimer type dementia in the early stages of the disease can be characterized by abnormalities but also by sparing of other cognitive mechanisms, particularly in memory and language. Nevertheless, many studies indicate an heterogeneity in cognitive profiles. This existence of subgroups of patients with Alzheimer type dementia would have important implications for therapeutic studies as well as investigations concerned with etiology.