Anthropometric and biochemical indices of nutritional status and weighed dietary intake have been studied in hospitalized patients with senile dementia, demented patients living in the community and age-matched control subjects who were not cognitively impaired. Demented patients were lighter than control subjects, and had a lower body mass index, skinfold thickness, mid-arm circumference and arm muscle bulk. The hospitalized patients were more seriously affected than those living in the community, and body weight was significantly negatively correlated with duration of hospitalization. Over a 6-month period the hospitalized patients showed a further weight loss, while those living in the community did not. Both groups of demented patients had higher intakes of energy, protein, vitamins and minerals than the control subjects. The diet of the hospitalized patients was slightly, but not significantly, superior to that of the patients living in the community. Biochemical evidence of specific vitamin inadequacy was equally prevalent in all three groups of subjects, and there were no significant correlations between the degree of cognitive impairment or behavioural disorder and any of the indices of nutritional state. Clinical signs suggestive of malnutrition were not correlated with either biochemical evidence of deficiency or cognitive impairment and behavioural disturbance.