We studied the proliferative ability of the marginal mucosal cells surrounding the ulcer in the healing processes of gastric ulcers. We obtained a labeling index (LI) at the neck and generative zone of gastric pit using a monoclonal antibody against DNA polymerase α for tractable and intractable gastric ulcers located at the fundic mucosa during each endoscopic stage. The LI during the healing stage was higher than that during the active stage in both the tractable and intractable cases. However, in each stage, the LI of the tractable gastric ulcers was higher than that of their intractable counterparts. Finally, we analyzed the LI in tractable gastric ulcers after setting two groups: one treated with anti-ulcer drugs and the other untreated. There were no significant differences between these two groups. We believe that investigation of proliferative abilities in the marginal mucosa of gastric ulcers is important to understand the nature of gastric ulcers and to assess therapeutic efficacy