A study designed to elucidate some of the special features and problems of ecclesiastical land ownership, through the medium of one of the leading English bishoprics, during a period of social and economic stress, coinciding with a phase of crisis and readjustment in the history of the Church. In spite of its palatinal jurisdiction Durham is found to be little different from the other bishoprics in terms of its temporalities. After a description of the bishopric estates and the manner of their administration, attention is turned to the phenomenon of an income which remained fairly static in an inflationary age, amidst conditions auguring growth. The bulk of the thesis is devoted to an examination of the resultant failure of the Bishops of Durham to become the improving landlords demanded by logic. Explanations are found in: the inadequacy of the antique administrative machinery as an instrument of improvement; the abandonment of entrepreneurial activity; the entrenchment of the tenantry behind beneficial conditions of tenure; the requirements of the patronage system made necessary by the Bishops' important, socio-political role, which put them at a disadvantage in management terms; the exploitation by powerful interests emanating from the State-Church relationship; the impediments to effective husbanding and regulation of resources inherent in the system of episcopal succession and the behaviour patterns characteristic of the episcopate; and the short comings of the counter-measures taken to arrest the administrative and economic defects. Overall it is clear that however desirable the efficient administration and improvement of the temporalities might have been, fulfilment of these twin objectives was rendered impossible by the power of the several countervailing considerations. In conclusion it is suggested that the Durham experience was fairly representative in its exposure to conditions which allowed for variation in detail within a framework of basic similarities