Regression testing is a well-established practice in software development, but in recent years it has seen a change of status and emphasis with the increasing popularity of agile methods, which stress the central role of regression testing in maintaining software quality. The objectives of this article are to investigate regression testing strategies in agile development teams and identify the factors that can influence the adoption and implementation of this practice. We have used a mixed methods approach to our research, beginning with an analysis of the literature to identify research themes related to the adoption of regression testing techniques under agile methodologies, from which we developed an analytical framework for the study. This was followed by three exploratory case studies that we used to exercise the main elements of the framework, develop some key themes of interest, and devise a questionnaire for the final stage of the study, an on-line survey to explore the main issues identified in the case studies across different contexts. Within our specific sample, our results suggest that organizational maturity is a key factor in effective regression testing practices and that the adoption of such practices is helped by a coherent testing philosophy and change management processes. We also found that the return on investment in automated regression testing was positive for our respondents and that adopting these practices in the context of agile methods had been a relatively painless process for the organizations in our survey. We conclude that investing in regression testing tools and processes is likely to be beneficial for organizations. However, further work is needed in assessing how organizational culture impacts on the quality process and the financial outcomes for commercial software development organizations.