The cell-cell-adhesion molecule E-cadherin is necessary for the maintenance of the epithelial cellular structure. We were able to show a correlation between decreasing E-cadherin expression, dedifferentiation and increased invasiveness in a cell line model. We studied 73 squamous cell carcinomas from the upper aerodigestive tract using the immunofluorescent method to demonstrate expression of E-cadherin. Decreased E-cadherin expression correlated with a decreased grade of differentiation and an increased lymph node metastatic rate. This confirms the significance of E-cadherin as a marker for differentiation and invasiveness of squamous cell carcinoma of the pharynx and larynx.