This study is desinged to aid in making clear the close relationship between the ovarian and adreanl functions by observing the changes of circulating eosinophils in conjunction with sexual cycles of female albino rats which weree under such stresses as subcutaneous injections of 3% formalin solution or electric shocks. For the control, a group of rats were observed without any stress. The results of the observations were as follows: 1) Numbers of circulating eosinophils in the rats under various expcrimental stresses were obviously diminshed, but there were no significance in the changing, rates in accordance with the stages of their sexual cycles as seen in control group. 2) In the group given a single injection of 3% frmalin solution, cosinophils showed marked decrease on the average -65.0% (-73.5% to -59.4%) 6 hours after the injection. On the second day of the injection, the number of eosionphils returned to subnormal level, being average rate of decrease -6.4% (-21.5% to +10.6%). When the injection were repeaied, recovery of the number of cosinophils from marked reduction occurring immediately after the first injection was much slower as the number of repeated injection increased. 3) In the group given a single electric shock, cosinophil showed reduction in number on the average -59.6% (-63.3% to -51.6%) 6 hours after the shock. On the third day of the electric shock, they showed moderate recovery, being average rate of the decrease -27.7% (-39.9% to -13.9%). As electric shocks were repeated, the reduction in number of the eosinophils was diminished and the recovery to normal become rapid and complete.