This thesis examines the doctrine of positive prescription of landownership in Scots law, with particular reference to the written deed that is required in order to commence the prescriptive period. The first part of the thesis sets out the historical context in which this doctrine has developed. Due to the civilian foundations of Scots law, the thesis begins with a brief examination of the Roman law of acquisitive prescription. This examination is both historical and comparative as it emphasises the unusual nature of the Scots law doctrine of positive prescription in comparison to Roman and later civilian formulations of acquisitive prescription. The fact that the Scots law of positive prescription has an apparent antipathy to good faith is also analysed in this context. The Roman law examination is then followed by a description of the development of the Early Scots law of acquisitive prescription. This again demonstrates the difference of Scots law from both civilian acquisitive prescription and common law adverse possession. The Early Scots law material is also significant in illuminating the context in which the Scots law doctrine of positive prescription emerged. The existence of limitation based on possession alone is a feature of Early Scots law which is highlighted in this section. The second, and more extensive, part of the thesis focuses on doctrinal analysis of the written deed that is required in order to commence positive prescription in Scots law. This is in turn divided between an examination of the requirement of ex facie validity of the foundation writ and an examination of the requirement that the foundation writ must be habile to include the area in respect of which positive prescription is sought. The thesis demonstrates that the development of the doctrinal formulations of these concepts has not been free from some degree of confusion. However, it is shown that, in the case of ex facie validity, there is a solid principle of interpretation, grounded in consistent authority, which has only fallen from view in recent times. In the case of hability, the underlying principles are not so easily discerned. Nevertheless, it appears that particular principles may be present in respect of the interpretation of hability. The thesis concludes with a discussion of the current and future state of the law of positive prescription of landownership, with particular reference to the impact of land registration.