The diagnosis of oral cancer based on histological examination is usually straightforward, substantial lesional/tumoral tissue is present in the biopsy specimens so it results in difficulty of early diagnosis. Therefore, it is so important to search for a sensitive and specific biomarker for early diagnosis can ensure the strategy of treatment, then avoiding multiple biopsies resulting in delay of treatment. Insulin-like growth factor-II mRNA binding protein 3 (IMP3) is a newly identified oncofetal mRNA- binding protein that binds 5' UTR of the insulin-like growth factor II leader 3 mRNA and may repress translation of insulin-like growth factor II during late development. The goal of this study is to establish the expression pattern and diagnostic value of IMP3 in oral squamous cell carcinoma and high-risk precancerous tissue and to determine whether IMP3 can serve as an early diagnostic and prognostic biomarker. Hence, the level of IMP3 expression in oral precancerous lesions and oral cancers from Department of Oral & Maxillofacial Surgery, Chi-Mei Medical Center by IHC and RT-qPCR assays were examined to accomplish this goal.