This paper provides a new assessment of Caesar's activity in north-east Italy, both in the 50s BC and in the aftermath of the Civil War, and discusses it against the background of the earlier Roman presence in the region and of the developments that intervened in the following generation. Its main contention is that Caesar carried out a number of important political and administrative interventions, both in Histria (chiefly through the foundation of the colony of Pola) and in the Alpine and pre-Alpine regions, marking a fundamental shift in the quality of the Roman presence in the area. The discussion falls under five headings: the value of the evidence of Caesar's Commentarii for his activity in north-east Italy; an overview of the problems for which inadequate documentation survives (such as the early history and legal status of Tergeste); the date and background of the colonisation of Pola; the changes in the administrative and agrarian setup of Histria and north-east Italy in the late Republican period; and the resulting economic and social developments in the region.The conclusions summarise the main insights emerging from a very fragmentary field of evidence, and seek to explain the inclusion of Histria in the Augustan discriptio of Italy with the exceptional prosperity of the region, which Caesar's interest had contributed to chart and exploit more effectively.It is well known that Julius Caesar had a major impact on Northern Italy, not merely because of the citizenship grant he bestowed on Transpadana in 49 BC, but more widely through the activity he carried out during his provincial command over the preceding decade. However, his work in the north-eastern fringes of the region has received comparatively less attention.A treatment of Caesar's impact on north-east Italy entails at least two preliminary problems.Much of what will be discussed in what follows will pertain to the last few years of Caesar's life, and will involve reconsidering one of the most intensely debated and least satisfactorily documented issues in ancient history: the ambitions that Caesar entertained and the objectives that he pursued, especially after his victory in the Civil War, as well as the factors that informed his strategy on a number of fronts. Moreover, the notion of north-east Italy requires some qualification. It retains its validity, of course, as a 'geographischer Ausdruck', a 'geographical expression', to borrow Prince Metternich's famous dictum, in the study of any historical period. However, it is far from apparent that in Caesar's time the territory on which this study will predominantly focus was regarded as part of Italia.The analysis developed in this paper reflects the highly fragmentary nature of the surviving body of evidence, and falls under five headings. It will open with a survey of the evidence for Caesar's activity in north-east Italy during his governorship (58-50 BC), and will then engage with some important, if woefully under-documented, aspects of the history of region at this time: the coexistence be...