Abstract: To investigate expression of Slit2 and its correlation with microvessel density in human hypopharyngeal squamous cell carcinomas, and to analyze their influences on the biological behavior of human hypopharyngeal squamous cell carcinoma. MethodsExpressions of Slit2 and CD34labeled microvessel density (MVD) were measured by immunohistochemical staining (Envision), and expression of Slit2 mRNA in 24 cases of fresh tissues was determined by reversetranscript polymerase chain reaction. ResultsThe positive rates of Slit2 in cancerous tissues and paracancerous tissues were respectively 65.2% and 40.5%（χ2=6.329，P<0.05）. Slit2 mRNA expressions between them also had statistical significance (t=8.230, P<0.05). Expression rate of Slit2 and enumeration of MVD were significantly associated with tumor size，TNM stage, and lymph node metastasis. Enumeration of MVD was increased in Slit2positive tissues（t=2.273, P<0.05）. Expression of Slit2 had a positive correlation with MVD（rs=0.430，P<0.05）. ConclusionExpression of Slit2 and enumeration of MVD are significantly higher in hypopharyngeal squamous cell carcinoma than in normal mucosa. They have significant relations to tumor invasion and lymph node metastasis，and the mechanism might be that Slit2 mediated new vessel formation in tumors.