Without a sufficient knowledge of the acute and late normal tissue reactions due to radiotherapy, a general practitioner is sometimes helpless and hopeless, facing a patient consulting with questions, or side effects. How to manage a skin reaction, a mucositis, a leucopenia, a hair loss, ...? The aim of this paper is to describe the pathogeny of frequent acute and/or late reactions related to ambulatory radiotherapy, allow an early diagnosis, facilitate a follow-up in common and provide guidelines for the symptomatic medical treatment.