BACKGROUND: The rising volume of referrals to secondary care is a continuing concern in the NHS in England, with considerable resource implications. Referral management centres (RMCs) are one of a range of initiatives brought in to curtail this rise, but there is currently limited evidence for their effectiveness, and little is known about their mechanisms of action. This study aimed to gain a better understanding of how RMCs operate and the factors contributing to the achievement of their goals. Drawing on the principles of realist evaluation, we sought to elicit programme theories (the ideas and assumptions about how a programme works) and to identify the key issues to be considered when establishing or evaluating such schemes. METHODS: Qualitative study with a purposive sample of health professionals and managers involved in the commissioning, set-up and running of four referral management centres in England and with GPs referring through these centres. Semi-structured interviews were conducted with 18 participants. Interviews were audio-recorded and transcribed. Data were analysed thematically. RESULTS: Interview data highlighted the diverse aims and functions of RMCs, reflecting a range of underlying programme theories. These included the overarching theory that RMCs work by ensuring the best use of limited resources and three sub-theories, relating to how this could be achieved, namely, improving the quality of referrals and patient care, reducing referrals, and increasing efficiency in the referral process. The aims of the schemes, however, varied between sites and between stakeholders, and evolved significantly over time. Three themes were identified relating to the context in which RMCs were implemented and managed: the impact of practical and administrative difficulties; the importance and challenge of stakeholder buy-in; and the dependence of perceived effectiveness on the aims and priorities of the scheme. Many RMCs were described as successful by those involved, despite limited evidence of reduced referrals or cost-savings. CONCLUSIONS: The findings of this study have a number of implications for the development of similar schemes, with respect to the need to ensure clarity of aims and to identify indicators of success from the outset, to anticipate scheme evolution and plan for potential changes with respect to IT systems and referral processes. Also identified, is the need for further research that evaluates the effectiveness and cost effectiveness of particular models of RMC.