Changes to the epigenetic information within a cell play a significant role in cancer development and progression. These epigenetic changes are important in establishing the aberrant gene expression patterns that are a feature of cancer cell biology. We are currently experiencing a rapid advance in our understanding of how epigenetic information is written and interpreted in the cell, and the enzymes involved in these processes have been recognised as prime targets for therapeutic intervention. Reagents that target these enzymes have the potential to inhibit or reverse epigenetic changes in cancer cells. Evidence suggests that the aberrant regulation of two gene silencing pathways; involving DNA methylation and histone methylation, play an important role in cancer development. Considerable effort is being exerted in the development of inhibitors of these pathways. However, complex functional interactions exist between the DNA and histone methylation pathways, and these interactions will need to be considered in the design of inhibitory molecules. This review details current research into agents developed as inhibitors of these epigenetic pathways, focusing on the types of epigenetic modifications being targeted, interactions between these modifications and the use of these inhibitory agents in cancer treatment.