Reirradiation represent an unfrequent particular clinical situation. The risk/benefit ratio assessment must be taken into account, considering both clinical and dosimetric aspects. There is a relatively limited amount of preclinical data available to date and clinicians should cautiously perform reirradiations in selected indications. This review summarizes the experimental data available on reirradiation of normal tissues, the consequences on early and late toxicities as well as the intrinsic limitations of these models.