An investigation was made on the relationship between tooth size and morphological characteristics of teeth from the standpoint of generational differences within a short period. Dental plaster casts were obtained from 682 students, born in the period from 1941 to 1967. These casts were divided into two groups: 254 subjects born from 1941 to 1949 (Group I), and those born from 1956 to 1967 (Group II). The mesiodistal and buccolingual diameters of tooth crowns were measured. To evaluate dental traits, the standard reference plaque by Turner II was used. Results showed that Group II had larger mesiodistal diameters of tooth crowns than those of Group I, and there was a remarkable increasing trend in the buccolingual diameters. In dental traits, apparent generational difference between the two groups was noted in double shovel-shape (I1, I2, I1, I2), cusp 6 (M1), and labial convexity (I1, I2). The above changes in size and morphological traits of the teeth seemed to be related to the uptake of nutrition, particularly, protein and lipids, in the developmental stage of the dental germ.