DNA methylation is an epigenetic mark that is associated with the repression of genes and transposable elements. In Arabidopsis, maintenance of DNA methylation is carried out by three methyltransferases: METHYLTRANSFERASE 1 (MET1), CHROMOMETHYLASE 3 (CMT3) and DOMAINS REARRANGED METHYLTRANSFERASE2 (DRM2). However, DRM2 is solely responsible for establishment of DNA methylation—or de novo methylation—. DRM2 is guided by small interfering RNAs, (siRNAs), in a process known as RNA-directed DNA methylation (RdDM). By a combination of genetic and biochemical approaches, we have Isolated and characterized several proteins acting with in the RdDM pathway. The role of these new proteins will be discussed.