To investigate the expression of NF-kappaB in acute leukemia and its relationship with P21, and matrix metalloproteinases (MMP), the expression of NF-kappaB, P21, MMP-2 and MMP-9 in bone marrow cells from patients with acute leukemia (AL) was detected using immunocytochemical technique. The results showed that the expression ratios of NF-kappaB, P21, MMP-2 and MMP-9 in untreated AL group were significantly higher than those in remission and normal control groups (P < 0.05), and no obvious difference was seen between remission and normal control groups. The expression of NF-kappaB was correlated with that of P21, MMP-2 and MMP-9 (r = 0.767, 0.729 and 0.803, respectively, P < 0.05). This study indicated that P21 protein, encoded by oncogene Ras, and NF-kappaB were super-expressed in leukemia cells. In conclusion, after activation by Ras, NF-kappaB combined with the kappaB sequences of MMP-2 and MMP-9 genes, then upregulated their expression. MMP might enhance the degradative function of leukemic cell, thus to make cells easier to cross through the bone marrow barrier and release into blood.