Adenosine-to-inosine (A-to-I) deamination is a functionally important modification of RNA that occurs in many metazoan nuclear transcripts, in several types tRNAs, and in mitochondrial transcripts of diplonemid protists. Several conceptually different methods exists to identify inosine residues in RNA,\u00a0including the approach that exploits the cleavage after a guanosine or inosine residue by RNase T1. The digestion at Gs is blocked after an incubation in a glyoxal\/borate solution and leads predominantly to cleavage 3\u2032 to Is. This protocol blends the procedure originally conceived by Morse and Bass (DOI: 10.1021\/bi9709607) and its more recent adaptation of Cattenoz et al. (DOI: 10.1261\/rna.036202.112).