Chromatin modifications are important for all cellular processes that involve DNA, including transcription, replication and DNA repair. Chromatin can be modified by the addition of adducts to histone tail residues or by nucleosome remodelling, which requires ATP-dependent chromatin-remodelling complexes. Although the role of these mechanisms in transcription is well studied, their impact on DNA repair has only recently become evident. One crucial chromatin modification, the phosphorylation of histone H2A, links the recruitment of histone modifiers and ATP-dependent chromatin-remodelling complexes to sites of DNA damage.