AIM: To investigate the significance of NAD (P)H-quinone oxidoreductase 1 (NQO1) protein overexpression for prognostic evaluation of ovarian mucinous cystadenocarcinoma .METHODS:NQO1 protein was detected in 162 cases of ovarian mucinous cystadenocarcinoma , 35 cases of ovarian mucinous cystadenoma and 29 samples of normal ovarian epithelial tissues by the method of EnVision immunohistochemical staining .The correlation between high expression of NQO1 protein and clinicopathological features of ovarian mucinous cystadenocarcinoma was also evaluated .Overall sur-vival and disease-free survival rates of ovarian mucinous cystadenocarcinoma patients were calculated by Kaplan -Meier method.RESULTS:The positive rate and strongly positive rate of NQO 1 protein were 85.8%and 64.2%in ovarian mu-cinous cystadenocarcinoma , respectively , which are significantly higher than those in ovarian mucinous cystadenoma , and normal ovarian epithelial tissues ( P <0.01 ) .NQO1 expression was significantly correlated with the histological grade (P<0.05) and clinical stage (P<0.01) of ovarian mucinous cystadenocarcinoma .Kaplan-Meier survival analysis showed that the overall survival rate and disease-free survival rate were significantly higher in ovarian mucinous cystadenocarcinoma patients with high NQO1 expression than those with low NQO1 expression (P<0.01).CONCLUSION:NQO1 expression is closely correlated with the progression and prognosis of the patients with ovarian mucinous cystadenocarcinoma .High ex-pression of NQO1 protein may be used as an important indicator for the patients with poor prognosis of ovarian mucinous cystadenocarcinoma .