Objectives: To discuss the character of relationships between operational and research staff and the necessary conditions for successful experiments. Methods: A review of research and experience in the conduct of experiments, especially randomized controlled trials, examining the foundations for success, issues in maintaining cooperation with operational staff, implementation and leadership issues. Results: The fundamental issue in successful experiments is the relationship between the operational and research entities, which most often resemble a coalition of temporary common interests rather than a partnership between parties with long-term common goals. Conclusion: Experiments require close cooperation between the parties because of the need for maintenance and monitoring. Researchers who use field trials have solved many of the common problems faced by those embarking on experiments and those who do so will be rewarded by the quality of their findings. Relationships which may be characterised as temporary coalitions for a common purpose may, under the right conditions, ultimately mature into true research partnerships.