BACKGROUND: Angiogenesis is a critical factor in the progression of solid tumors and metastasis. The aim of this study was to characterise the roles of angiogenic and anti-angiogenic factors on ovarian cancer. METHODS: The expression levels of vascular endothelial growth factor (VEGF, angiogenic factor) and pigment epithelial growth factor (PEDF, anti-angiogenic factor) were measured by real-time polymerase chain reaction and Western blotting in ovarian tumors. Microvessel density (MVD) was evaluated by the total microvessel length in high-power field of tumor tissue preparations. RESULTS: MVD correlated with tumor malignancy. The tissues with the highest expression levels of VEGF (VEGF-H) were malignant tumors. The VEGF expression levels in some malignant tumors (VEGF-L) were as low as that in benign tumors. Therefore, the expression of PEDF was examined. The PEDF expression levels in VEGF-L malignant tumors were significantly lower than those in benign tumors. On the other hand, the PEDF expression levels in VEGF-H malignant tumor tissues were not significantly different from those in benign tumors. CONCLUSION: The reduction in PEDF expression levels may be, in part, responsible for tumor malignancy in VEGF-L ovarian tumors. Furthermore, PEDF may be a useful marker of malignancy in VEGF-L ovarian tumors.