ADAR1 and ADAR2 are members of a family of enzymes that catalyze the conversion of adenosine to inosine in double-stranded RNA. Unlike the other types of RNA editing that involve multiprotein editing complexes, the site-specific deamination of an adenosine to inosine is catalyzed by single enzymes. ADAR1 and ADAR2 have been purified and the genes cloned from various sources. Each gene encodes multiple splice variants. As it is crucial to have an adequate supply of pure protein to investigate this type of RNA editing, we describe in this article methods for both the purification and the overexpression of either full-length or partial ADAR1 and ADAR2 isoforms.