The study of 186 cases (bed rests) of patients who have had a therapeutical radiotherapy shows that: those who have received a thoracic irradiation (neo-breast) do not release an appreciable hypereosinophilia (2% of cases); those who have received a pelvic irradiation (neo uterus, testicle, ovary) set a mode-rate hypereosinophilia (from 450 to 1 000 eosino/mm3) in 90% of cases; in Hodgkin's disease, 15% of the patients have an hypereosinophilia before any treatment; it increases to 34% after radiotherapy (cobalt 60); No difference has been shown either with the site of radiation (up or under the diaphragmatic) or with the age of the patients. On the other hand, a significative prognosis (survival greater than or equal to 5 years). From these observations, the authors propose some physiopathological hypothesis on the signification of hypereosinophilia in the course of therapeutical irradiations and Hodgkin's disease.