The potentials of the two major histological types of gastric carcinoma to invade through extracellular matrices were studied with cell lines. We found that the invasive potential of intestinal-type carcinoma cells (MKN-28 and MKN-74) were higher than those of diffuse-type carcinoma cells (MKN-45 and KATO-III). To investigate whether the alpha 2 and alpha 6 integrin adhesion molecules are responsible for, or involved in carcinoma invasion. We further studied alpha 2 and alpha 6 expression patterns in these two types of cell line. Although fluorescence-activated cell sorting analysis revealed that all cells examined invariably expressed these integrin molecules, their expressional patterns were different among different cell lines. The intestinal-type carcinoma cells expressed integrins mainly along the cell-cell contact region, whereas the diffuse-type carcinoma cells showed a diffuse cytoplasmic pattern of integrin expression. Invasion by MKN-28, MKN-74 and MKN-45 cells through reconstituted basement membrane or type I collagen gel was significantly inhibited (P < 0.05) by 50 micrograms/ml anti-(alpha 2 integrin) or anti-(alpha 6 integrin) monoclonal antibodies. Our results suggest that active invasiveness is stronger in the intestinal-type than in the diffuse-type carcinoma cells and that alpha 2 and alpha 6 integrins play important roles in invasion of both types of gastric carcinoma cell lines.