The effect of neonatal androgenization with testosterone propionate (TP) on growth, food intake, and feeding circadian and ultradian rhythms was studied in male and female rats. TP-female rats but not TP-male rats weighed more and ate more in adulthood than control animals injected with oil. TP administration to male rats induced few changes in the circadian organization of food intake and meal size. However, neonatal androgenization of female rats produced an approach of feeding parameters to those showed by male rats: diminished meal number and increased meal size and food intake. Moreover, the spectral analysis of meal frequency revealed that TP induced in female rats an enlargement in the 4.8 h ultradian component. Although hormone secretions produced in adult animals contribute to sexual dimorphism, it is noticeable that androgen presence during the organizational period is largely responsible for differences between sexes.