Results of the analysis of the body proportions of a group of 258 “normal” young men, investigated by the Grant Study of Harvard University, indicate an association between restricted ranges of the body ratios called disproportions, and the frequency of certain dominant personality traits. The disproportions here studied are: Stature tall for body weight Shoulders broad for circumference of chest Chests narrow for width of shoulders Chests shallow (front to back) for width of shoulders Hips broad for width of shoulders Heads large for size of chest Chests small for stature Leg circumferences small for width of shoulders Faces broad for width of chest Hands large for body weight Hips broad for width of chest Individuals possessing these disproportions have a greater frequency of those dominant personality traits indicating lesser stability, lesser integration, greater sensitivity and complexity of the personality, and lesser capacity for making easy social adjustments. Some of the traits which go with the disproportions are “unstable autonomic functions,” “less well-integrated,” “mood fluctuations,” “bland affect,” “inhibited,” “cultural,” “lack of purpose and values,” “inarticulate,” and “asocial.” Conversely, individuals with traits indicating “soundness,” stability, integration, vitality, and strength of personality have fewer disproportions in their physiques than the average of the group. These generalizations are supported by analyses of a large series of unselected undergraduates rated on the basis of general “soundness” of personality, and a group of students who were referred to the college psychiatric clinic. In both instances the disproportions were more frequent in the “less sound” undergraduates and in the psychiatric clinic cases. It is suggested that the disproportions are constitutional and as such may indicate a genetic element in the determination of personality and behavior. However, it is pointed out that verification of this supposition must await further study with other groups, in different age levels, and in varying cultural settings.