Recent studies of formal structure in themes in the Classical repertoire (William Caplin) as well as the music of Wagner (Matthew BaileyShea) point towards the enormous importance and potential of the Sentence phrase structure with its hybrid forms for analyzing tonal music. Initially described by Schoenberg, a Sentence is phrase consisting two main events of equal length, a presentation phrase (consisting of one repeated basic idea) and a continuation phrase. In this paper I will demonstrate Bartók's dependence upon Classical and Romantic phrase structures, including the Sentence, and also the Classical Period (consisting of an antecedent and consequent phrase). In both his small-and large-scale works, Bartók's sentences display a Classical coherence, despite the lack of a functional harmonic framework, due to their clear formal articulation and clearly defined modal pitch centers. Bartók also utilized chains of Sentences, Satzketten, in several works including Concerto for Orchestra. I will describe the different paradigmatic types utilized by Bartók in works such as Divertimento, the String Quartets, along with the Violin and Piano Concertos. Particularly significant is how Bartók alters the repeated basic idea and elaborates the continuation phrase and the creation of compound forms.