The extant text of the Galenic commentary on the Hippocratic treatise On Humours has been considered a Renaissance forgery composed by Giovanni Battista Rasario. This text consists of an amalgamation of former works blended by the author without a linguistic reelaboration, including sections written in the non-literary koine of the second century BC. The analysis in this paper of part of Kühn’s edition distinguishes between emendations, glosses, lacunae and different types of changes, before urging the need of a total revision to achieve a satisfactory establishment of the text.