A great part of the perceived value of history in the ancient world was connected with its educational function. In one way or another, it was regarded as a beneficial guide to conduct or as magistra vitae (Cicero, De Oratore II, 36). To give political instruction and advice on the one hand (Polybius, I, 1, 2), and to provide exempla, were two major aims of history. This paper will argue that by narrating the history of the past, historians not only judged past actions or people, and provided useful moral examples to their contemporaries, but also stimulated a type of competition between past and present times. By recording good examples to be imitated and bad ones to be avoided, the Roman historians promoted the code of values of the maiores for their own time, fostered action and, to a certain extent, became significant indicators to Roman society. This competitive aspect of Roman historiography is illustrated here in three distinct categories, analysing the work of major Roman historians: Sallust, Livy and Tacitus.