In 27 BC, Augustus split up the provinces into two great classes: the newly-won provinces, which needed the presence of the Roman army and came under the emperor's jurisdiction; and the others, which came under the Senate's jurisdiction. This division was not an absolute one, however, which is why numerous provinces were, for various lengths of time, under the jurisdiction of one or other constitutional partner. The most important difference between them, was the presence of Roman troops in the Imperial provinces (only), and the absence of Roman legions in provinces governed by equestrians. The unique exception to the latter was Egypt.

The provinces of Asia and Africa were governed by proconsuls; the remainder by praetors. Though the Senate appointed proconsuls, it was the emperor who, by virtue of his imperium proconsulare maius ('major proconsular powers'), had the right to intervene tactically in the appointment of governors.

The Imperial provinces were divided into those whose governors came from the Senate as Imperial ambassadors (legati augusti pro praetore), and those which (from the mid-first century AD onwards) were governed by equestrians -the so-called prefects or procurators. Both ambassadors and prefects/procurators were appointed by the emperor and, unlike other officials, were not bound by the institution of service for a period of one year, but remained in their province until recalled by the emperor himself.

Every governor was accompanied to his appointed province by a certain number of advisers and staff, who were known as his comites ('companions'), the number apportioned being proportionate to his social standing. Nevertheless, if he was to govern at all effectively, he would have to work closely with the local officials, since it was essential to take note of the provincial people's traditions and sensibilities.

The administrative system of provincial organization was perhaps the most representative example of the way Roman political theory was put into practice, a theory which did not favour the separation of administrative, legislative, judicial and military responsibilities. Governors seldom acted off their own bat or intervened in local authorities' decisions, economic affairs being possibly the one exception to this rule.