Plasma and red-cell folate levels and dietary folate intake were monitored for about six months, including two months during which supplementary vitamin C was given, in 21 healthy elderly men and women living at home in the north of England. Although biochemical values were consistently low in some subjects, no clinical folate deficiency was detected. Dietary folate intake was significantly correlated with red-cell folate, but not with plasma folate. Before vitamin C supplementation, folate intake was significantly correlated with vitamin C intake, and plasma, but not red-cell, folate was significantly related to plasma and buffy-coat vitamin C levels. During the period of vitamin C supplementation, no significant changes in plasma or red-cell folate levels were detected, even in subjects who had low initial levels of circulating vitamin C.