In the fourth book of his de Doctrina Christiana, Augustine delves into his theory of preaching and enters into dialogue with the three rhetorical styles of Cicero. He explains that Christian preaching also ought to utilize different styles, but the Christian preacher's three styles are not the same as the classical orator's three styles. After describing his theory, Augustine presents examples of the Christian styles from other Christian preachers. This paper considers consistency between Augustine's theory and practice. Since Augustine was a prolific preacher, the question arises: when Augustine preached, did he follow his own theory of preaching as outlined in de Doctrina Christiana? Furthermore, how does the amount and type of consistency between Augustine's theory and practice contribute to an understanding of the development of his theory? Did this treatise flow from his experience over years of preaching, or did he have his theory of preaching in mind at the outset and only later write it down? The question of whether and in what ways Augustine follows his own guidelines for preaching in the three styles can be illuminated by a close reading of Enarrationes in Psalmos 69, a transcript of a sermon preached by Augustine. Chapter one of this paper explores Augustine's description of each style and examines excerpts from En. Ps. 69 that adhere to his descriptions, asking whether the three styles are, in fact, able to be distinguished from one another. Chapter two considers one specific aspect of style, prose rhythm, to determine how Augustine uses it as he preaches, and whether it helps him achieve his goals in preaching. Chapter three examines the overarching structure of the sermon, showing that he views his task primarily as an exultation of the martyrs rather than simply an exegesis of Psalm 69. Each of these inquiries sheds light on the question of how well Augustine's practice of preaching adheres to his ideas as outlined in de Doctrina Christiana.