This article looks at the relationship between economic regulation, environmental regulation, company strategy and the environment in the UK water and sewerage industry. The regulatory field in this industry, following privatization in 1989, is highly complex and interdependent. The paper presents three case studies of company interpretation of and response to changes in this regulatory field, focusing particularly on the third review by the economic regulator, in 1999, which involved a reduction of the prices companies were allowed to charge their customers. This had significant but complex repercussions for environmental strategy and management in the companies, with different impacts on mandatory and non-mandatory activities. It also showed in relief the opportunities for building coalitions between companies and the environmental regulator, both in general terms and revolving around specific, local environmental issues and schemes. Companies' strategic direction was also found to have an impact on their response to the regulatory review. Copyright © 2007 John Wiley & Sons, Ltd and ERP Environment.