Objective: Fluorescent In Situ Hybridization (FISH) was used to evaluate Chromosome 17 aneusomy and p53 aberration in resection margins of oral squamous cell carcinoma (SCC). Materials and Methods: Twenty-six oral SCC cases were obtained from the Department of Oral Pathology, Oral Medicine and Periodontology, Faculty of Dentistry, University of Malaya and Institute for Medical Research, Kuala Lumpur from the years 1984 to 2003. Four micro thick paraffinized sections were stained with Hematoxylin & Eosin (H&E) for detailed histological examination. FISH was performed using DNA specific probe of centrometric region of chromosome 17 and LSI p53 (17p13.1). Hybridized signals were scored in at least 200 nuclei under 100x oil immersion objective using Fluorescent microscope. T-test and Chi-square test were performed to analyze the data. Statistical significance was obtained at p<0.05. Results: Mean FISH signals for chromosomy 17 probe in test sample were 44.5±12.8 for monosomy 17, 41.0±10.2 for disomy 17, and 14.5±10.1 for polysomy 17. Mean FISH signals for p53 probe in test sample were 48.9±9.7% for monoploidy, 41.0±9.5 % for diploidy, and 10.2±7.8% for polyploidy. Statistical significant relationship was found between chromosome 17 aneusomy and p53 aberrations (p=0.019). Conclusion: This finding suggests that numerical abnormality of chromosome 17 and p53 aberration occur during the development of oral SCC as observed by FISH. Therefore, FISH can be used as a tool for evaluating neoplastic activity at the surgical margin of oral SCC. This study was supported by the University of Malaya, Vote F Grant F00210/2003A.