Since nutritional deficiencies might worsen the severity of symptoms and prolong the length of illness in non-nutritional disorders, particularly in the elderly, we examined the nutritional status of 216 elderly women newly admitted to a mental hospital. Compared to healthy elderly women, they had lower values for plasma prealbumin, vitamin C, and B vitamins. This was particularly common in senile dementia, and appeared to be the result of inadequate intake of protein or vitamins. Regular hospital diet for one month corrected the very low levels of prealbumin, but supplements were essential to remove deficiency of the water-soluble vitamins. Although vitamin supplements did not influence the length of stay in hospital, we did not exclude the possibility that nutritional deficiencies have a significant effect on the severity of mental illness.