The role of telomeres and telomerase in oral cancer is an area of much recent interest. The understanding of the role of telomere biology, the end replication problem leading to genomic instability and the reactivation of telomerase is absolutely critical to our understanding of oral cancer, and more so, to our ability of early diagnosis and developing novel therapies and cancer prevention approaches. The aim of the present study was to quantify telomerase activity in oral squamous cell carcinoma and normal oral mucosa and assess the role of telomerase as diagnostic and prognostic marker of oral malignancy. This book describes a research on quantification of telomerase activity in oral squamous cell carcinoma tissues. The results of the present study indicate that activation of telomerase activity is frequent in oral cancer. Statistically significant difference in quantified telomerase levels of OSCC and normal oral mucosa demonstrate the significant clinical usefulness of telomerase activation as a valuable marker for diagnosis, while significant correlation of telomerase activity with grades of malignancy indicate its effectiveness as marker for prognosis of OSCC.