Suetonius’ treatise “On Insults" is the sole surviving ancient work on the subject of verbal abuse, yet it still lacks a proper critical edition, an extensive commentary, a translation in a modern language, and only a handful of studies were made of its text. After reconstructing the text, I will study the opusculum both from the sociolinguistic and from the lexicographic point of view. The organization of lemmata, not in alphabetical order, but by semantic categories, yields us thirteen types of people targeted by typical insults in Greco-Roman literature: old people, hypersexual men and women, effeminate men, bad commanders, people from other ethnic groups, braggarts, unintelligent people, sycophants, rustics, gluttons, slaves, and an additional category of poneroi, a rather vague insult which we could translate as "rogues" or "good-for-nothings," which covers all the terms of abuse which do not fit in the categories above. The study of these insults will yield interesting information from the sociolinguistic (diaphasic and diastratic variation), morphological, semantic points of view. I will also analyze the treatise as a lexicon, paying attention to how definitions are formulated, how paretymologies are derived, and what words are grouped together. Finally, I intend to examine what other lexica contain the same lemmas and how their definitions differ: this will help to contextualize Suetonius's work in the Greek lexicographic tradition.