In order to elucidate the role of alpha-smooth muscle actin (ASMA)-positive stromal cells, namely myofibroblasts (MFs), in invasive growth of gastric carcinomas (GCs), we examined the number of MFs at the deep border (DB) of GCs. In total 78 invasive GCs (48 intestinal type GCs and 30 diffuse type GCs) were examined immunohistochemically, and analyzed from the view point of tumor depth and histological type. In the intestinal type GCs examined, both the GCs confined to the submucosa and muscularis propria had none or a small number of MFs at the tumor border facing the submucosa (smDB) and muscularis propria (mpDB), respectively; whereas the GCs invading the subserosa had a moderate or large number of MFs at the tumor border facing the subserosa (ssDB) (p<0. 05). Regardless of tumor depth, the diffuse type GCs examined generally had none or a small number of MFs at the smDB, mpDB and ssDB, respectively. There is a possibility that intestinal type GCs invading the subserosa showing tubular and papillary structure may induce myofibroblastic transformation of gastric subserosal stromal fibroblastic cells.