This chapter explores the relationship between Horace’s Ars Poetica and Dionysius’ On Composition. The first part presents a general comparison of Dionysius and Horace, their place within Augustan Rome, and their literary theories. The second part concentrates on what may be called the central theme of composition theory in both Dionysius and Horace: the idea that the most beautiful style is achieved by a skilful arrangement of common words. While some of the parallels between the Greek critic and the Roman poet can be explained by their use of common sources and (Peripatetic and Hellenistic) traditions, other parallels suggest that the two authors were familiar with notions and ideas that were circulating in Rome. The ideal of a skilful arrangement of common or normal words, which is characteristic of the Augustan Age, can be related to the self-presentation of Augustus and to the ancient perception of Virgil’s poetic style.