This thesis addresses changes in the layout of the agricultural landscape in Ulster from the 17th to the mid-19th century. Rural Ireland underwent considerable change during this period, with rundale - a type of openfield farming - giving way to the network of regular, enclosed fields present throughout most of the country today. This work draws on data gathered from archival cartography and supporting documentation to record and analyse patterns and progress from a variety of case-studies. Geographic Information Systems (GIS) was employed to carry out the investigation. Extant work on the Ulster landscape during the period in question is dated and has tended to focus on marginal areas of the country. It has been presumed that the patterns observed in such marginal piaces must apply throughout the country. The use of GIS in this thesis brings the research topic up-to-date, enabling accurate processing of large volumes of data. This was not previously possible. A new methodology for the application of GIS in the Irish context was developed. The case-studies selected for analysis are situated in more fertile, central locations than the areas addressed in the extant literature. This enabled comparison with the marginal places investigated in earlier work. Conclusions could therefore be drawn regarding the accuracy of the assumption of a fairly homogenous process of change between the 17th and 19th centuries in Ulster. The case-studies were also set in context with agricultural change in England and Scotland. The work undertaken in this thesis is of value not only within academia, but also in relation to the creation of policies for landscape management and conservation.