Thin layer chromatography was investigated using inorganic as well as organic adsorbents with special reference to vitamin B_<12>. The reference standards of vitamin B_<12> analogues used were cyano-and hydroxo-cobalamin, pseudo-vitamin B_<12>, factors A, B, and III. Adsorbents examined were Aluminium oxide G, Kieselgel G, and Kieselgur G as inorganic ones, and P-and DEAE-cellulose as organic ionexchangers. It seems that each adsorbent requires adequate solvent systems for a selective separation of each vitamin B_<12> factor, and can be practically used depending upon the purpose. The conditions for improving separation were also discussed.