A-to-I RNA editing, the important event of gene modification, which takes place at post-transcriptional level, was firstly reported in 1991. The molecular mechanism of A-to-I RNA editing involves site-selective deamination of adenosine to inosine in pre-mRNA, which leads to altering translation codons and splicing in nuclear transcripts, thereby functionally distinct proteins can be produced from a single gene. The mammalian editing enzymes ADARs (adenosine deaminases acting on RNA) are widely expressed in brain and other tissues, however, up to date their substrates are mainly found in the central nervous system. It has recently been noticed that imperfect editing of these RNA substrates play critical roles in corresponding diseases, indicating that A-to-I RNA editing may be quite important in physiological or pathophysiological processes. Finding more new substrates of ADARs, especially in peripheral tissues, and performing functional research on new genes will be helpful to elucidate the biological significance of A-to-I RNA editing.