RNA editing by adenosine deamination is a posttranscriptional mechanism for the regulation of gene expression and is particularly widespread in mammals. A-to-I RNA editing generates transcriptome and proteome diversity allowing organisms to produce many more gene products and functions than predicted based on the number of genes within their genome. Also, it regulates important functional properties of neurotransmitter receptor genes in the central nervous system by changing single codons in pre-mRNA. The deficiency or misregulation of editing has been implicated in the etiology of neurological diseases, such as epilepsy, amyotrophic lateral sclerosis (ALS), depression and tumor progression. Widespread A-to-I modification of repeat sequences in the human transcriptome suggests additional roles for RNA editing and links it to other processes of gene regulation, such as RNA splicing as well as siRNA mediated gene silencing and miRNA function. Here, I am reviewing main features of this epigenetic phenomenon, its relevance for health and disease, as well as potential prospects for using RNA editing as a therapeutic tool.