Mizuki Ozawa and Akio Inoue: Relationship between diameter growth pattern and spatial distribution in an even-aged pure stand of Japanese cedar (Cryptomeria japonica D. Don). Jpn. J. For. Plann. 57: 3～13, 2023 The relationship between diameter growth pattern and spatial distribution of individual trees was quantitatively analyzed. In an even-aged pure stand of Japanese cedar (Cryptomeria japonica D. Don; ca. fifty-year-old), the stem position was recorded, 196 cedar trees were felled, and then the annual ring at breast height was measured. Twelve growth functions were fitted to the diameter growth of each individual, with the Richards function being the best fit. Based on the parameters of the Richards function, a hierarchical cluster analysis was performed, indicating that it was optimal to divide all trees into two classes. Comparison of the parameters between the classes demonstrated that two classes were defined as the fast and slow growing trees with different diameter growth pattern. Using the L-function, the spatial distribution of the trees was examined by classifying all trees into four classes based on the diameter growth pattern (fast and slow growing trees) and diameter size at felling (larger and smaller trees). As a result, it was found that (1) While the fast growing trees with larger diameter (F-L trees) were uniformly distributed, the F-L and other trees were distributed exclusively; and (2) The slow growing trees with large and small diameter were concentrated ipsometrically. These findings are beneficial when predicting the stand growth by considering the spatial distribution of individual trees.