It is now widely recognised that epigenetic changes are implicated in human cancer. Epigenetic information in chromatin (known as the 'histone code') has been proposed to extend and modulate the genetic (DNA) code in the regulation of key cellular processes. Histone modifications and histone modifying complexes have been traditionally associated with transcriptional regulation; however, recent studies indicated that the mechanisms involving the histone code play important roles in DNA replication, DNA damage detection and DNA repair. The histone code is believed to be 'read' by cellular machineries to regulate accessibility to, and functions of, chromatin DNA and the disruption of this code may lead to diseases, notably cancer.