Three-old seedlings derived from seeds collected from individual tree across Japan and local one as control were planted out at Tsugawayama Experimental Forest for Cryptpmeria Breeding in 1944. These families were classified into 3 groups according as their bole volume growth, namely superior, median and inferior ones at the age of 42 in 1983. Fifty trees selected from 3 families for each group and from the control were subjected to stem analysis. Using the values obtained from stem analysis, we calculated normal form factors every 5 years from 15- to 40-year old, and then analyzed the difference of stem form among 10 Cryptomeria families. Generally, mean normal factors in each family had been increasing sharply for 10 years from 15-year old, and gradually after that. There are the various types of changes of the factors over time, however. As a results of the analysis of variance by one-way layout with the factor of the family and the test by multiple comparisons, there are significant differences among the families at every ages, but the number of combinations with significant differences decreases as the trees grow older. There is no tendancy that the more superior tree growth is, the larger normal form factor is, and vice versa.