An oncogene is a modified gene, or a series of nucleotides that encode a protein, and direct the cell to the development of a neoplastic phenotype. Usually, oncogenes are involved in tumour development and increase the possibility that the development of a cell directs towards cancer. In this book, the authors present current research in the study of the classification, mechanisms of activation and role in cancer development of oncogenes. Topics include the role of oncogenes in gynaecological pathology; oncomirs as the next frontier of oncogenes affecting cancer aetiology and tumour progression; the role of the epidermal growth factor receptor as a therapeutic target in glioblastoma and other malignancies; and tumour suppressers involved in DNA repair and carcinoprevention.