Abstract: Malignant transformation is a complex multistep process involving numerous genetic changes, which include loss of tumor suppressor gene function, oncogene activation and alteration of modifier genes. During the past decade, evidence has accumulated in support that FHIT, as a new tumor suppressor gene, plays a roll in many tumors. In this review, described the recent findings in the molecular biology of FHIT, with particular focus on its relationship with radiation carcinogenesis.