Purpose: The purpose of this study was to examine the effects of the ulmus root-bark dressing on tissue regeneration in experimentally-induced pressure ulcers in rats. Method: A randomized pretest/post-test control group time-series study design was used. Thirty-three male Sprague-Dawley rats were used in this study. The rats were anesthetized with 100mg/kg of ketamine. Pressure ulcers were induced at 140mmHg for three hours using a personally-designed pressing apparatus. For four weeks, the ulmus root-bark dressing was applied every other day in the experimental group (n=18) and a wet gauze dressing in the control group (n=15). For data analysis, the statistical program SPSS WIN 12 was used. The wounds were examined by light microscopy andelectron microscopy. Result: There were significant statistical differences in the size of the pressure ulcers as time went by(p=0.006). It should be noted that there were no significant statistical differences in the number of capillaries. Using light microscopy the inflammatory infiltration and neovascularization in the dermis in the experimental group emerged densely in the early stages, but recovered rapidly at the latter stages. In addition, the reepithelization of the epidermis occurred earlier than in the control group. By electron microscopy, the cell organelles of the capillary endothelial cells and the basal lamina of capillaries in the experimental group showed a more rapid maturation during the latter stages, compared with the control group. Conclusion: According to this study, it can be concluded that the ulmus root-bark dressing is effective regarding the healing of pressure ulcers.