Eleven sugi cultivars in 20-year-old stands were sampled to quantify the tracheid lengths for juvenile wood and mature wood. Tracheid lengths of latewood were estimated from macerated tissue in every ring at the breast height of three to five trees in each cultivar. Tracheid lengths of every cultivars were initially short near the pith and increased outwards within about 15 rings from the pith, as shown in Fig.1. The result was that the tracheid length of the 16th ring was regarded as the representative value of tracheid length in mature wood. There were high correlations between tracheid lengths of juvenile wood and the tracheid length of the 16th ring from the pith, and the decision coefficients for correlations were shown in Fig.2 and Fig.3. However Figs.4 and 5 show that the plots of rings near the pith for cv. obiaka and cv. hinode deviate from the regression lines, and the tracheid lengths of these rings may be unsuitable for predicting the tracheid length in mature wood. In the 8th ring from the pith, there was no cultivar deviated markedly from the regression line of the tracheid length of the 16th ring on tracheid length of a given ring in juvenile wood as shown in Fig.9.