The aim was to study secular changes in head dimensions of Japanese adults. The age range of the subjects was between 18 and 25 years. Four head measurements were taken: head length, head breadth, head height and head circumference. The present sample was compared with the series taken between 1910 and 1917 of Matsumura (1925) for both sexes, the one measured in 1965 of Morita and Ohtsuki (1973) for male and another measured in 1975-1979 of Ohtsuki and Ito (1980) for female. The present study demonstrated the presence of larger means for head length, head breadth and cephalic index in the current sample than in their predecessors of about 35-85 years ago. Also, the present series displayed larger head circumference than that of the Morita and Ohtsuki series. Using ANOVA, head length and head breath showed significant (p<0.01) differences among all birth-year cohorts from 1978 to 1983 of the current sample. Head height, head circumference and cephalic index did not display significant differences. However, the slope of the regression line indicated that all measurements as well as the cephalic index showed slightly decreasing tendencies during the investigated period.