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This study is focused on the identification of gene mutations in H-ras which are probably associated with tumor recurrence in oral squamous cell carcinoma (OSCC) following conventional therapy.Surgically removed biopsies from OSCC patients without recurrence (n = 43) and biopsies from recurrent cases (n = 19) were analyzed. Also, gingival tissues (n = 5) from normal individuals were processed and considered as control. DNA was extracted and amplified using primers for exons 1 and 2 for the H-ras gene, and then DNA products were analyzed using Sanger's sequencing technique. Besides, H-ras expression was compared in samples by immunostaining (IHC), using anti-ras antibody.Demographic data show that smoking habit in patients and recurrent tumors was ~ 44.1 and 78%, respectively. The major site of malignancy was tongue tissue (40-60%). The rate of pathological stage III/IV were 41.8 and 100% in primary tumors and recurrence malignancy respectively. The sequencing data showed that a specific mutation in H-ras gene, Gly12Ala (G6266A) in recurrence samples and primary cases was detected in ~ 66.6% and 10% respectively. Accumulation of H-ras protein in tissues was relatively high scores ( 5) in both primary and recurrence tumors. The H-ras mutation detected was associated with increased level of H-ras protein accumulated in the malignant cells (IHC data).These data may suggest that regardless of the causes and factors involved, Gly12Ala (G6266A) is associated with recurrence in high-grade OSCC tumors.