Endothelin-1 (ET-1) is a potent inducer of peptic ulcers. The roles of ET-1 in ulcer healing, however, have remained unclear, and were investigated in mice. Gastric ulcers were induced in mice by serosal application of acetic acid. Three days later, the mice were given a neutralizing ET-1 antibody or non-immunized serum. The ulcer size, amount of fibrosis and myofibroblasts, and localization of ET-1 and ET_A/B receptors were analyzed. To elucidate the mechanisms underlying the effects of ET-1, we examined the proliferation, migration, and release of growth and angiogenic factors in gastric myofibroblasts with or without ET-1. Expression of prepro-ET-1 (an ET-1 precursor) and endothelin converting enzyme-1 was examined in gastric myofibroblasts using RT-PCR. Immunoneutralization of ET-1 delayed gastric ulcer healing. The areas of fibrosis and myofibroblasts were smaller in the anti-ET-1 antibody group than in the control. ET-1 was expressed in the gastric epithelium, myofibroblasts, and other cell-types. ET_A receptors, but not ET_B receptors, were present in the myofibroblasts. ET-1 increased proliferation and migration of gastric myofibroblasts. ET-1 stimulated the release of hepatocyte growth factor, VEGF, PGE₂, and IL-6 from gastric myofibroblasts. mRNA for prepro ET-1 and endothelin converting enzyme-1 was also expressed. ET-1 promotes the accumulation of gastric myofibroblasts and collagen fibrils at gastric ulcers. ET-1 also stimulates migration and proliferation of gastric myofibroblasts, and enhances the release of growth factors, angiogenic factors, and PGE₂. Thus, ET-1 has important roles not only in ulcer formation, but also in ulcer healing via mobilizing myofibroblasts and inducing production of stroma-derived factors.