The term valetudinarium refers to the hospital in Roman times. The word derived from the Latin word valetudo, that mean "good health". These structures were built along the borders “limes” since the time of the Emperor Augustus, and as military hospitals within each legionary or auxiliary castrum.

We know very little about military surgery in the Republican age. Authors who testify before Augustus, as Livio, say that the wounded in battles were brought in villages near the conflict areas for treatment. It was essential to intervene in time to treat infections caused in the clash with means and appropriate treatment.

With Augustus reform of the army were introduced military doctors who had received, as opposed to those civilians, a specific training. It was also of vital importance to have a good health condition of the soldiers, and permanent camps (castra stative) placed near rivers, far from unhealthy areas, such as the malarial swamps or in arid regions, not shaded by trees, or difficulties in supply helped.

Among  many examples of valetudinarium we can find visible traces in the legionary fortress of Vindobona, to Carnutum, to Aquis Querquennis in Roman Spain.

Normally the valetudianrium was of rectangular shape. In the middle there was a large courtyard and along the four sides were positioned medical lanes for patients, formed from many rooms (where they were admitted to the sick and wounded of war; to Inchtuthill there were 60 of 4 x 5 meters each), both along the inner perimeter (which overlooked the courtyard) and along the outer. Among the series of internal and external rooms there was a wide corridor as it is still possible to see in the legionary fortress of Inchtuthill in Britain. Some of these rooms were later used by the administrative staff, medical and nursing staff. For instance in Novaesium and Castra Vetera at the entrance of valetudinarium there was a large great room used as hospital "reception".

The size could vary, unlike the legionnaire’s camps, the valetudinarium of the auxiliary were of smaller dimensions. Indeed, we know that at Housesteads there was one of the largest military hospital (18 meters x 27 meters). The structure was different from those of the legionnaires. In Fendoch, for example, there was a rectangular building with a central corridor.

The Roman Army had great interest in maintaining the health of their people, developing a sophisticated medical services, based on the best medical knowledge of the ancient world. The Roman army had highly qualified doctors with a huge practical experience. Although their knowledge was entirely empirical, not analytical, their practices were strictly controlled and tested on the battlefield, and therefore more effective than those available to the majority of armies since nineteenth century.

The prefect castrorum was the General manager of the medical staff and related services of a legion. Under his command was the optio valetudinarii, or director of the military hospital of the legionary fortress, which was the administrative officer of the medical staff. There were also capsarii (nurses valets), frictores (masseurs), ointment, curatores operis (insiders to pharmaceutical services). However, head of clinical service there was a service "head doctor", simply called Medicus.

The cavalry had their physicians (doctors alarum) as well as in the marina there were doctors triremis. There was also a gradation of military doctors in medicus legionaris higher order medicus cohorts, and finally the medicus ordinarii who had the rank corresponding to the centurion, but without an actual command of the soldiers.