The effect of removing the ovaries from mice at two months of age on the subsequent aging changes in the uterus was investigated by means of two tests: (1) Stromal cell proliferation in response to ovarian hormones, and (2) the response of the uterus to a decidual stimulus (intraluminal arachis oil) after suitable hormone treatment. Entire animals of the same age and young animals were used as controls. The decline in the response to a decidual stimulus occurred at the same age in animals which had been ovariectomized at puberty as in those which had remained intact. In both groups, at 15 months of age, there was a significant decrease in the amount of decidual tissue formed in comparison with the young animals. The stromal cells, however, were still able to divide in response to ovarian hormones in both groups. It was concluded that, as far as these tests could determine, removal of ovaries early in life did not affect the onset of aging changes in the uterus.