Two patients with iron overload and liver disease had folic acid deficiency. In one patient it was associated with elevation of serum iron level and reappearance of iron in hepatic cells. Treatment with folic acid was followed by decrease in both serum and hepatic cell iron levels. In the other patient folic acid deficiency was associated temporally with the onset of diabetes mellitus and with a severe and fatal bout of right-sided cardiac failure. The clinical courses of these patients suggest that folic acid deficiency may influence the tissue distribution of iron in man in a manner analogous to that demonstrated in experimental animals.