Abstract: Objective To explore the relationship of the expressions of MDM2 and MMP-9 in osteosarcoma with the pathological parameters and prognosis of the tumor.Methods The expressions of MDM2 and MMP-9 were detected with immunohistochemical(S-P)method in specimens from 61 cases of osteosarcoma.The correlation between the expressions of MDM2, MMP-9 and pathological characteristic, metastasis and prognosis was analyzed statistically.While 20 cases of normal osseous tissue were used as negative control group.Results The positive rates of MDM2 and MMP-9 in osteosarcoma were higher than those in the normal osseous tissue respectively(P＜0.001).The expression of MDM2 and MMP-9 were not correlated to the sex, age and pathological grades of the osteosarcoma(P＞0.05), but correlated to tumor metastasis and prognosis(P＜0.05).The five-year survial rate in patients with positive expression of MDM2 and/or positive expression of MMP-9 was significantly lower than that in negative control group(P＜0.001).The patients with positive reaction for both MDM2 and MMP-9 had the lowest survival rate, the difference was significant(P＜0.001).Conclusion There is an intimate correlation between the overexpression of MDM2 and MMP-9 in osteosarcoma and it is useful parameter to evaluate prognosis of osteosarcoma.