DNA repair is a process vital to the cell since the genetic material is the target of a multitude of daily attacks. Cells have evolved into possessing distinct but simultaneously intercalating ways of dealing with repair of DNA lesions. These repair pathways may include practices dealing with single strand damage (Base Excision Repair, Nucleotide Excision Repair, Mismatch Repair) or with double strand damage (Non-homologous End Joining and Homologous Recombination) as well as Direct Reversal Repair and Translesion Synthesis. The present chapter deals with one of these pathways (Base Excision Repair), which rectifies damage at the point of the single nucleotide.