Dysregulation of the epigenome plays a fundamental role in tumour development. Epigenetic events are a major mechanism for inactivating tumour suppressor and DNA repair genes and occur ubiquitously during the early stages of tumour development. Unlike genes inactivated by mutation, genes silenced epigenetically are intact and potentially responsive to reactivation by small molecules. This review discusses the potential for restoring epigenetic balance as a means to prevent cancer.