Objective: The expression of vascular endothelial growth factor (VEGF) is correlated to the invasion and metastasis of tumor cells in many clinical carcinomas. In this study, we detected soluble VEGF levels in ascites and peritoneal fluid and explored its clinical significance. Methods: A total of 91 samples were collected and divided into 5 experimental groups: petitoneal fluid of patients with benign (n=10) and malignant disease (n=14), cirrhotic ascites (n=36), tuberculous ascites (n=8) and malignant ascites (n=23). Using a sandwich enzyme-linked immunoadsorbent assay, the concentration of soluble VEGF was measured in ascites (n=67) and petitoneal fluid (n=24). Results: VEGF levels in malignant ascites were 640.74±264.81 pg/ml, significantly higher than those in cirrhotic ascites, tuberculous ascites and peritoneal fluid of patients with benign and malignant disease (P<0.01, separately). However, the difference of VEGF levels among the latter 4 groups had no statistic significance (P>0.05), separately). Furthermore, VEGF levels in malignant ascites from patients with ovarian cancer were higher than those with gastric and colon cancer (P<0.01, respectively), while there was no significant difference between gastric cancer and colon cancer (P>0.05). Using VEGF level of 118.96 pg/ml as a minimum cutofflimit, the sensitivity and specificity of VEGF of this assay to diagnose malignant ascites were 91.3% and 73.9% respectively. Conclusion: The elevated levels of VEGF may be useful as an index in differential diagnosis of benign and malignant ascites. It appears that VEGF plays an important role in malignant ascites formation.