Objective: The purpose of this study is to examine the role of versican (VCAN) in advanced stage serous ovarian cancer by investigating its expression, its function, and its correlation with clinical outcomes. Methods: Microarray analysis was performed on RNA isolated from tumor and stromal components of advanced stage serous ovarian cancer and normal ovarian epithelial tissue to identify genes up-regulated in ovarian tumor stroma. Validation studies using immunohistochemistry and quantitative real-time PCR (Q-RT-PCR) was performed on one of the up-regulated genes, VCAN. Immunolocalization of VCAN (n = 111) and CD31 (n = 56) was done on serous ovarian tumors. CD31 staining was performed to examine microvessel density (MVD). Q-RT-PCR was performed on 65 samples to evaluate the differential expression of VCAN isoforms. Cell proliferation and invasion assays were performed to examine how V1-treated ovarian cancer cell lines and an endothelial cell line would differ from controls. Univariate survival analyses were done with VCAN expression. Correlation analysis was done with CD31, platinum resistance, and clinical data. Results: Validation studies using Q-RT-PCR and immunohistochemistry showed significantly higher VCAN V1 isoform expression in ovarian cancer stroma compared with normal ovarian stroma and ovarian cancer cells. Correlation studies showed stromal VCAN expression was associated with poorer overall and progression-free survival, platinum resistance, and increased MVD. VCAN-treated ovarian cancer and endothelial cells showed increased invasion potential. Conclusions: VCAN overexpression is associated with increased MVD and invasion potential, which may lead to poorer overall and progression-free survival and platinum resistance. © 2010 Elsevier Inc.