DNA repair is implemented through a large variety of mechanisms, each of them being adapted to a specific type of lesion: direct repair, mismatch repair for the errors occurring during the replication process, base-excision repair, nucleotide-excision repair, double-strand breaks DNA repair by homologous or non-homologous recombination. Each of these mechanisms involves numerous proteins associated as supramolecular functional complexes. Some anticancer drugs are able to generate DNA lesions which may overflow the repair mechanisms. The impossibility to repair DNA damage usually leads to cell death, but alterations of repair mechanisms may favour genetic instability and hence contribute to oncogenesis.