E-cadherin, Ca(2+)-dependent intracellular adhesion molecule, is known to be an invasion suppressor gene. To elucidate the correlation between E-cadherin expression and invasion or metastasis in gastric cancer, we examined E-cadherin tissue status immunohistochemically. Ninety-eight primary gastric cancer, prepared by AMeX method, were retrospectively analyzed with anti-E-cadherin monoclonal antibody. In normal gastric epithelium, E-cadherin is expressed homogeneously with a typical membranous staining at cell-cell borders. Decreased and heterogeneous expression is found in 70 of 98 tumours. Tumours with decreased E-cadherin expression had a tendency to infiltrate more deeply in stomach wall, and metastasize in lymph nodes or peritoneal surface. More importantly, decreased E-cadherin expression correlates with shorter survival (z = 3.98, P = 0.00086). These results may indicate that E-cadherin tissue status is a powerful prognostic indicator in gastric cancer. The high malignant potential of tumours with decreased E-cadherin expression may be associated with high potential of lymph node metastasis and peritoneal dissemination.