The pinning method for the measurement of xylem growth was modified for easier application. Trunks of Chamaecyparis obtusa were monthly incised with a knife instead of a thin needle. Two years later, xylem blocks including wounded areas were harvested. For comparison, circumferential increases of the same trees were measured with a banddendrometer. Measurements from the wounding method indicated a tendency for cambial cell production to accelerate twice a year, around April and August. Circumferential increase measured with the banddendrometer differed from radial growth measured from wounding. Circumferential increase was very small around August and continued after the cessation of cell production. The c1imatic data near the plantation suggested that the circumferential size of the trunk probably is affected by the physical shrinkage of trunks because of water shortage during drought season and trunk swelling following precipitation. Circumferential increments did not reflect the seasonal rhythms of xylem growth. Therefore, for detailed information on radial growth within a season, the wounding method is recommended.