Matrix metalloproteinases (MMPs) are known to play an important role in cancer cell invasion by mediating the degradation of extracellular matrix proteins. The activity of such MMPs are regulated by tissue inhibitors of metalloproteinases (TIMPs). In this study, we investigated the immunohistochemical expression of MMP-2, MT1-MMP, TIMP-2, MMP-9, and TIMP-1 in 114 epithelial ovarian tumors (14 adenomas, 22 borderline tumors, and 78 adenocarcinomas). mRNA expression of MMP-2, MT1-MMP, and TIMP-2 was determined by RT-PCR in selected samples. The diffuse positive rates of MMP-2, MT1-MMP, TIMP-2, and MMP-9 in ovarian carcinomas were significantly higher than those in the borderline and in benign tumors. Conversely, the diffuse positive rate of TIMP-1 was higher in the benign and borderline ovarian tumors than that in ovarian carcinomas. The percentages of the cases with triple diffuse positive expression for MMP-2, MT1-MMP, and TIMP-2 within the same tumor was significantly higher in malignant tumors than those in borderline and in benign tumors. With respect to clinical stage, the triple diffuse positive rate in advanced-stage (stage II/III/IV) carcinomas was significantly higher than that in early-stage (stage I) carcinomas. A significantly higher triple diffuse positive rate was also observed in high-grade (grade 2/3) disease than in low-grade (grade 1) disease. Considerable levels of mRNA expression of MMP-2, MT1-MMP and TIMP-2 were detected in all selected samples that showed triple diffuse positive immunostaining, confirming the co-expression of MMP-2, MT1-MMP, and TIMP-2 at the transcriptional level within the same tumor. All cases with diffuse positive expression for MMP-9 showed regional or negative TIMP-1 expression. The diffuse positive rate of MMP-9 was significantly higher in ovarian carcinomas with lymph node metastasis than in those without lymph node metastasis. Our results suggest that the overexpression of MMP-2, MT1-MMP, TIMP-2, and MMP-9 and down-regulation of TIMP-1 may contribute to the development or enhanced growth capacity of ovarian tumors. Co-expression of MMP-2, MT1-MMP, and TIMP-2 within the same tumor seems to play an important role in the progression of ovarian cancer. Elevated MMP-9 expression together with low expression of TIMP-1 may also contribute to the lymph node metastasis of ovarian carcinoma cells.