E-cadherin is a cell to cell adhesion molecule which acts as a suppressor of metastasis. This study examined the effect of gamma-linolenic acid (GLA), a n-6 polyunsaturated fatty acid, on the expression of E-cadherin in human cancer cells. Western blotting studies demonstrated that treatment of cells with GLA for 24 h increased the expression of E-cadherin in lung, colon, breast, melanoma, and liver cancer cells, but not in endothelial cells and fibroblasts. The results were confirmed by immunocytochemistry. In contrast, two other n-6 fatty acids, linoleic acid and arachidonic acid, failed to induce these changes. The increased expression of E-cadherin was correlated with reduced in vitro invasion and increased aggregation, indicating that the increased E-cadherin expression induced by GLA was biologically active. These data add GLA to the short list of E-cadherin up-regulatory factors. The up-regulation of E-cadherin expression in human cancer cells may contribute to the anticancer properties of GLA.