This study has been primarily based on data arising from the draining loans under the mid-nineteenth-century land-improvement legislation, relating to the whole country, and from the adoption of draining on estates in Devon, Northamptonshire and Northumberland. The data represent a marked advance on the sources, secondary contemporary accounts and questionable surrogate measures of land drained, employed in much present-day literature to determine the extent and effect of the improvement. As with so many aspects of nineteenth-century agriculture, too much emphasis has been placed on anecdotal evidence on draining, with little attempt being made to accumulate relevant and precise data on the improvement. For draining in particular, reliance on anecdotal material poses real problems, for the perception of the improvement underwent radical revaluation in nineteenthcentury agricultural literature. The enthusiasm for the new draining systems and materials around 1840 stimulated extravagant and untried claims for the improvement in the fields of cost, permanence, rental return, yield output and farming practice. When these expectations failed to materialize, there was a reaction to the improvement, its efficiency and productivity being doubted most notably in the 1873 report of the Select Committee of the House of Lords on the improvement of land. Such biases inherent in much of the contemporary literature preclude the attainment of any satisfactory assessment of draining as a nineteenth-century agricultural improvement and merely serve to perpetuate the divergence of present-day opinion. However, the draining-loan and estate data, although not allowing a full reconstruction of draining activity, provide at both the national and local level a consistent and reliable basis initially to clarify the adoption of the improvement and subsequently to assess its value in the development of nineteenth-century English agriculture.