Trials of educational or organizational interventions to change clinical practice require cluster randomization, that is, randomization of units such as hospitals or clinical teams rather than individual patients. Cluster randomization is relatively novel in health care settings and raises new methodological challenges, in particular: are units willing to be randomized at an organizational level; and, what procedures should be followed to successfully enrol all of the clinicians in a unit rather than individual clinicians as in conventional multicentre trials. This is particularly problematic for trials of large units such as hospitals. The aim of this study was to develop and partially evaluate a strategy to recruit acute, secondary care NHS hospitals in the UK into cluster randomized trials. Literature search and interviews with senior staff in acute hospitals and relevant national organizations were used to develop a recruitment strategy. The strategy was evaluated by inviting 32 randomly selected clinical directorates to participate in a trial feasibility study. A seven step recruitment strategy was developed: (1) Identify stakeholders and gatekeepers; (2) Inform stakeholders and gatekeepers; (3) Approach gatekeepers; (4) Local negotiation; (5) Conduct the research; (6) Feedback to gatekeepers; (7) Feedback to stakeholders. Key problems were the possibility of multiple gatekeepers and identification of all possible stakeholders in varying organizational structures. The strategy was effective in two respects. First, 32 (100%) of the directorates approached agreed to participate. Second, baseline data collection was successfully achieved in all of the directorates. However, the strategy is costly in terms of time and resources. We conclude that NHS trusts are willing to participate in cluster randomized trials. This recruitment strategy is successful and could be widely adopted, but realistic time and financial cost estimates are required at the planning stage.