This thesis explores various aspects of the medical system, and illness/disease for the medieval period (5th-12th centuries) in Ireland. On examining three archival source-types (hagiographical material, annals, medico-legal law texts), it became clear that there were different perspectives on health and healing for this period. Two distinguishing models came to light, a „Christian (religious) explanatory model‟ and a „Naturalistic Model‟. The former model centered mainly on the hagiographical material and elements related to Christian doctrine; however, aspects of this model were found in the annals also. The latter model was to be found in the annals and medico-legal law texts; both sources provided naturalistic aspects in relation to cause, cure/treatment and the legalities of illness and injury. The anthropological literature acted as a valuable interpretative tool when addressing these models and the processes of healing which took place. For example, the hagiographical material contained much religious symbolism in relation to illness causation and healing; the annals displayed symptomatic, prophylactic and naturalistic elements related to cause of illness; the medico-legal texts contained naturalistic aspects also; however, they came from a different perspective, they centred on the legalities of the medical system and took an empirical approach to cure. This thesis aims to convey how these two models, which were composed of three perspectives, when combined provided a picture of the health care system in medieval Ireland. These sources individually outline a range of illnesses, injuries and plagues; they also demonstrate the existence of healers. The anthropological literature has enabled this system to be placed in a particular cultural context; it has allowed us to see a medical system which was composed of different parts, yet function and act as one system. A second and no less important element of this thesis is the connection that is conveyed between the medical system and other institutions in society; the medical system acted as a window into the entire order of society.