We previously described the metabolism of 1,25(OH)2D2 into various side chain hydroxylated metabolites formed as a result of C-24, C-26 and C-28 hydroxylations in rat kidney24. We now demonstrate c-24 hydroxylation of 1,25(OH)2D2 in human leukemic cells and also present evidence to show that C-24 and C-26 hydroxylations either alone or in combination do not significantly alter the effect of 1,25(OH)2D2 on these cells, while C-28 hydroxylation reduces its activity. We previously described the metabolism of 1.25-(OH)2D2 into various side chain hydroxylated metabolites formed as a result of C-24, C-26 and C-28 hydroxylations in rat kidney24. We now demonstrate C-24 hydroxylation of 1,25-(OH)2D2 in human leukemic cells and also present evidence to show that C-24 and C-26 hydroxylations either alone or in combination do not significantly alter the effect of 1,25-(OH)2D2 on these cells, while C-28 hydroxylation reduces its activity.