The aim of this study is to evaluate the expression of vascular endothelial growth factor (VEGF) and its soluble receptor (sFlt-1) in peritoneal fluid (PF), peritoneal endometriotic lesions and eutopic endometrial tissues of patients with endometriosis. Peritoneal fluid, peritoneal endometriotic lesions and eutopic endometrial samples from patients with endometriosis, and peritoneal fluid, peritoneal tissue and endometrial samples from patients without endometriosis were obtained during an operative laparoscopy. The mean PF concentrations of VEGF and sFlt-1 were significantly higher in patients with endometriosis than in the controls. In the peritoneal tissue, the expressions of VEGF and sFlt-1 were significantly higher, where the expression of sFlt-1 in endometrium was significantly lower in patients with endometriosis. These findings indicate that not only abnormal expressions of angiogenic factors, but also aberrant expressions of antiangiogenic factors in the peritoneal and endometrial environment seem to be involved in the pathogenesis of endometriosis.