1. Circulating levels of eosinophils in the monkey have been followed before and after total-body exposure to a near median-lethal dose of x-radiation.
2. Eosinophils are moderately decreased during the first three days and strongly depressed in the second and third weeks. During the fourth week these cells rapidly reappear, and an absolute and relative eosinophilia ensues which is maximal at the fifth to seventh week.