Weight loss is common in elderly people with dementia, particularly those with Alzheimer' disease (AD), and feeding difficulties are major issues in their care in the later stages of the disease. In this study (REAL FR for Réseau sur la maladie d'Alzheimer Français) we prospectively used the Mini Nutritional Assessment (MNA) to examine the nutritional status of 479 subjects. Three groups of patients were studied: group 1 = 22 patients with undernutrition (MNA = 17), group 2 = 166 patients with risk of undernutrition (17 < MNA < 24), and group 3 = 291 patients without undernutrition (MNA = 24). Correlations with behavioral and psychological signs and symptoms of dementia (Neuropsychiatric Inventory NPI), with caregiver distress (Zarit), and with the Mini Mental State Examination (MMSE) were studied. Undernutrition is more frequently associated with low MMSE (p < 0.001), high behavioural disturbances (p < 0.001) and high distress of caregivers (p < 0.001). Risk of undernutrition is also associated with NPI (p < 0.001) and Zarit (p < 0.001). These first results in a French cohort of patients with AD underline the importance of the evaluation of nutritional status and finally the follow-up of eating behavior, cognitive status and the quality of life of the caregivers.