To establish the guideline for nutrition in the very old, we analyzed biochemical and hematological data from 45 Japanese centenarians living in Tokyo metropolitan area during 1994 and 1995. Levels of cholesterol, HDL-cholesterol, apolipoprotein A1 and B, albumin, prealbumin in serum were lower than in a control group or lower than the reference range, which indicates that these centenarians were undernourished. RBC counts, hemoglobin, and hematocrit were also low in the centenarians. The concentration of albumin correlated positively with those of HDL-cholesterol and apolipoprotein A1, and negatively with concentration of Lp(a). The value for transferrin correlated positively with energy intake and with the concentration of apolipoprotein A1. The concentration of prealbumin correlated positively with the concentration of hemoglobin, hematocrit and the total cholesterol concentration. According to their nutritional status, the centenarians were divided into 2 groups: well-nourished and undernourished. Those who were well-nourished had higher levels of cholesterol, HDL, Hb, and apolipoprotein A1, their levels of ADL and cognitive function were also high. The findings of blood-chemical data in the centenarians may be partly due to undernutrition. Centenarians who were well-nourished were considered to be aging successfully. These results and others previously published indicate that the concentrations of albumin, prealbumin, transferrin and either CRI or IL-6 are useful for nutritional assessment in the very old.