Abstract
A marked increase of total serum vitamin B_<12> level was recognized in patients with chronic myelocytic leukaemia among 23 cases of leukaemia tested. The increase of free vitamin B_<12> was largest in acute myelocytic leukaemia, and the higher values of the vitamin were obtained in patients with disturbed liver function. With regards to the relation between serum vitamin B_<12> and the findings in bone marrow as well as peripheral blood in patients treated with antileukaemia agents, no decision could be given, since there were only few cases dealt with.
