Observations on lowered excretion of vitamin B12 after intramuscular injection of 60 µg. of this vitamin in hepatic disease have been extended and confirmed. Except for some borderline cases in other diseases with possible involvement of the liver, we find low excretion in rheumatic heart disease as well as in lobar pneumonia, previously reported. The mechanism underlying the deviations from the normal situation in liver disease and rheumatic heart disease in respect to the vitamin B12 binding factor, to the serum protein composition, and the role played by the kidney is the subject of current studies.