The ability of selective absorption of the polypeptide transcobalamin II by silica gel was used for the determination of the unsaturated cobalamin binding capacity of haptocorrin and transcobalamin II. Two different silica gels, QUSO G 761 and FK 383 DS, were compared by Sephacryl gel-filtration and by determination of unsaturated haptocorrin and transcobalamin II from forty different patient sera. It was found that the silica gels act identically for this purpose.