A nutritional study was carried out of 16 independent-living elderly (9 women, 7 men) suffering from dementia and a control group matched for sex and age. The study consisted of interview (with participants or relatives/home helps), a 3-d weighed dietary record and biochemical determinations of blood components. No significant difference in mean daily energy intake between demented elderly (women 7.2 +/- 2.0 MJ, men 8.6 +/- 1.2 MJ) and controls (women 6.9 +/- 0.7 MJ, men 9.4 +/- 2.0 MJ) was found. The women with dementia had lower dietary intakes of protein (P less than 0.05), thiamin (P less than 0.05) and vitamin C (P less than 0.01) than female controls. For both sexes in both groups the nutrients most lacking were vitamin D and thiamin. Dietary supplements were more frequently used among elderly with dementia (50 per cent) than among controls (13 per cent) (P less than 0.05). Except for vitamin D, supplements did not reduce the number of demented elderly with low intakes (less than two-thirds of the recommendations) because generally those in most need were non-users. The demented elderly had lower levels of haemoglobin and folic acid (blood and plasma) (P less than 0.05) but better thiamin status (alpha-transketolase) than controls (P less than 0.05). No difference in mean levels of protein, 25-hydroxyvitamin D, vitamin E, vitamin B12 in serum was found. Individuals with blood or serum levels of nutrients below reference values were more frequently found among the demented elderly than among controls. In the dementia group 2 individuals with low levels of 25-hydroxyvitamin D also had clinical evidence of osteomalacia.