The allometric relationships between tree height and diameter of the following six native cultivars of sugi (Cryptomeria japonica) in Kyushu region are analyzed: Kumotooshi, Yaichi, Obiaka, Yabukuguri, Measa and Ayasugi, using the stem analysis data obtained from 21-year-old sugi cultivars in the experimental plots established in the Kyushu University Forest in Kasuya. The different allometric relationships are observed in the two-gradient before and after crown closure each cultivar, and then the relative growth coefficients are estimated each gradient. Both in the analysis of variance by one-way layout with the factor of the cultivar and the test by the multiple comparison method, there are significant differences among the cultivars each gradient. In consideration of the above results, the estimated relative growth coefficients each gradient and their changes in the gradient, the six cultivars are classified into the following three groups: 1) Kumotooshi, 2) Yabukuguri and Measa and 3) Yaichi, Ayasugi and Obiaka. From the results obtained, it is indicated that the models with different structures for the cultivar or the classified cultivar group are necessary for the construction of the system yield table of the sugi plantations.