The thesis examines the pollution of water by pesticides in Britain, an issue of public and political concern since the late 1980s as the results of extensive water monitoring, required under the EC's Drinking Water Directive have highlighted the spread and levels of contamination. The study explores the co-evolution of post-war agricultural policy and pesticide usage and examines how pesticide pollution of water has been constructed as a 'problem' and how this has been contested by different groups. Survey material from the Bedford Ouse catchment in Bedfordshire and Buckinghamshire is used to explain how farmers use pesticides, for what reasons, and with what understandings of the pollution risks their use brings. The questions to be addressed are: i) why, since the Second World War, have pesticides become such an important element of farming practice in Britain ? ii) how do farmers decide which chemicals to use and how to use them ? iii) how has pesticide pollution of water emerged as a 'problem' ? and iv) what are the implications for farming practices of regulations to tackle pesticide pollution ? Pollution is conceptualised as the outcome of a pollution production process' involving a network of actors, including farmers, advisors, scientists, pesticide manufacturers and regulatory agencies. Through an examination of farmers' actions in this context the thesis shows that, far from being the result of some natural technological progression, the increasing dependence upon pesticide technologies has been shaped and determined by broader social and political factors. The first part of the thesis explores the historical context for pesticide use in Britain, concentrating on the roles of agricultural policy and science and technology. In the second part, the actions of arable farmers are assessed through locally-based fieldwork conducted in 1991 in the catchment of the Bedford Ouse.