Objective To observe the expression of cyclooxygenase(COX)-2 in different malignancy astrocytoma by immunohistochemistry,so as to judge the invasive action of COX-2 in astrocytoma.Methods A total of 55 cases with astrocytoma underwent 63 times operation including 8 recurrent cases were selected,and 9 cases with severe brain injury who needed decompression surgery were selected as control group.The astrocytoma tissues and decompression surgery to remove tissues removed immediately fixed in 10％ formalin buffer solution.The expression of COX-2 was determined by immunohistochemistry.Results The positive expression rate of COX-2 in astrocytoma tissues was higher than that in decompression surgery to remove tissues[69.84％ (44/63) vs.1/9],and there was significant difference (x2 =11.589,P ＜ 0.01).The positive expression rate of COX-2 in recurrent astrocytoma tissues was higher than that in primmy astrocytoma tissues [8/8 vs.65.45％ (36/55)],and there was significant difference (x2 =3.957,P ＜ 0.05).With increased astrocytoma malignancy,the positive expression rate of COX-2 also increased,and there was significant difference (P ＜ 0.05).Conclusion COX-2 may have some relationship with the invasion of astrocytoma,leading to increase tumor grade,and relapse.