RNA editing is a collective term referring to a plethora of reactions that ultimately lead to changes in RNA nucleotide sequence apart from splicing, 5' capping or 3' end processing. Spread throughout the Eukarya, RNA editing creates genetic information de novo, alters decoding capacity, or influences structure and stability of RNA by inserting, deleting or modifying nucleotides. Evolutionarily unrelated, co-transcriptional or post-transcriptional mechanisms include RNA polymerase stuttering, guide RNA-directed cascades of nucleolytic and phosphoryl transfer reactions, site-specific deamination and others. Here, I discuss recent advances in the enzymology of various RNA editing systems, focusing on the diversity of mechanisms that change the RNA sequence in order to fulfill a specific biological function, even if the latter is not always apparent.