Anatomical changes in traumatic phloem resin canal formation induced in Chamaecyparis obtusa S. ' Z. were examined periodically after mechanical wounding. Five to seven days after wounding, the parenchyma cells close or closest to the cambium at the time of injury expand radially, and then between the seventh to the ninth day, the expanding parenchyma cells developed into tangential rows. Some of the cells simultaneously divided periclinally within nine to fifteen days after being wounded. Moreover, derivatives schizogenously separated from each other and continued to divide. The spaces were enlarged by tangential and radial division of parenchyma cells. The axial and ray parenchyma cells divided mainly periclinally and also anticlinally to form canals, and eventually, circular or elliptic resin canals c. 100 to 200 µm in diameter in regular tangential rows, separated by ray cells. Traumatic phloem resin canals form a tangentially anastomosing network.