The erythrocyte (RBC) ferritin content was measured in patients with chronic liver diseases including alcoholic liver disease, liver cirrhosis (LC) and hepatocellular carcinoma (HCC), and normal subjects as controls. The relationship between RBC ferritin content and iron deposition in hepatocytes was studied. The mean RBC ferritin content (MV +/- 1SD) from normal subjects was 20.7 +/- 9.7 ag/cell in male, 11.1 +/- 5.5 ag/cell in female (ag = 10(-18)g). RBC ferritin content from chronic liver disease was higher than that of normal subjects, especially in liver cirrhosis. It elevated to 71.0 +/- 52.2 ag/cell in male, and 41.6 +/- 35.0 ag/cell in female. The iron deposition in hepatocyte was observed mostly in patients with RBC ferritin content over 20 ag/cell. The microheterogeneities of RBC ferritin from liver cirrhosis was examined by isoelectric focusing (IEF) and compared with that of normal subjects. RBC ferritin from normal subjects was detected at pI range from 5.1 to 5.7 in most cases, while it was detected at pI range from about 5.0 to 6.0 in the liver cirrhosis. More basic ferritin was detected in the latter and the peaks of pI was also more basic than that of normal controls. Since patients with liver cirrhosis examined had iron deposition in hepatocytes, it is conceivable that the occurrence of basic ferritin reflects iron overload in the liver. Taking these results together, it was concluded that the presence of iron deposition in hepatocytes and the degree of iron overload can be assumed from the determination of RBC ferritin content, a noninvasive procedure.