Abstract: The trunk of Eucommia ulmoides Oliv. following ringing about one meter in length, could regenerate new bark without significantly affecting the tree growth. Such regeneration process differed from that following partial stripping in other trees as has been reported previously. After ringing in Eucommia ulmoides, there was primarily a proliferation of xylary mother cells and partly remained cambium cells forming a cork layer which led to the establishmant of a more or less normal complete periderm. At the same time the xylary ray cells near the surface dilated and proliferated until they extended across in continuity with the neighbor rays. No callus formation by the rays emerged from the surface was observed. Among the ray cells following multiplication, some immature xylary elements were also visible. Simultaneously, some immature xylary elements lying internal to region of the dilated and coalesced ray cells gradually transformed into new cambium. Due to the fact that initially part of the xylary ray cells was not completely differentiated, it seemed that some of the remained xylary rays separated the newly formed cambium zone into many segments. Three to four months after ringing, new cambium activity proceeded periclinally so as to establish a complete ring of cambium zone. Subsequent differentiation of newly formed cambium followed the normal pattern of vascular tissue development in this plant.