While our knowledge about effective (mental health) care is growing fast, transfer of this knowledge to practice and use in day-to-day patient care is often failing. Scientific evidence is increasingly summarized in systematic reviews (for example, by international Cochrane Collaboration working groups) and in clinical practice guidelines (thousands of guidelines are available around the globe). However, audits in different countries show that as many as 30% to 45% of patients fail to benefit fully from this development because they do not receive optimal (evidence-based) treatment.1-3 A large percentage of medications and tests administered to patients are unnecessary (estimated at 20% to 25%), and therefore costly and potentially harmful for patients. Transfer of scientific knowledge on appropriate performance in mental health care meets similar problems; for example, only one-quarter of patients with anxiety disorders in the United States received care in line with evidence-based treatment guidelines.4 A study5 in the Netherlands on patients with symptoms of depression showed both substantial over- and undertreatment with antidepressants. Widespread implementation of evidence-based care models for patients with severe mental illness failed until recently.6,7 In conclusion, concerning knowledge transfer to health care practice, we are dealing with a large and underestimated problem. Focused attention to the problem, and articles about possible ways forward in mental health care as presented in this issue,8,9 is an important step to explore and find solutions. The question of how to bring scientific knowledge more effectively into day-to-day practice is not an easy one to answer. Many policy-makers and practitioners have naive ideas about implementation of better mental health care. For instance, many have the expectation that if scientific knowledge is presented to mental health professionals in accessible formats with convincing arguments for their use that they will use it in practice. Some professionals will indeed do so, but most are influenced, most of the time, much more by other drivers, such as practical problems, organizational barriers, patients demands, avoiding unrest and conflict in their work setting, financial incentives, opinion of peers, and the wish to have a good time. This makes knowledge transfer, also in mental health care, a complex issue without straightforward answers. Overviews of the literature on effective knowledge transfer and implementation of evidence into practice (for example, Grol and Grimshaw,10 Grimshaw et al,11 and Grol et al, editors)12 showed that many different approaches and interventions to implement evidence into practice are used, some focusing on knowledge, attitudes, or routines of individual professionals (for instance, courses, conferences, feedback, reminders, outreach visitors, and opinion leaders), others on: influencing patient behaviour or patient demands to professionals; organizational changes to promote better use of evidence; or, economic or regulatory interventions to enforce following clinical guidelines. None of these approaches proved to be superior in all settings or for all problems, and even well-developed change programs had mostly only moderate effect (8% to 10% change in key targets). For many new types of change interventions (such as the breakthrough collaborative model, pay-for-performance initiatives, leadership enhancement, and patient empowerment), the number of well-designed studies is very limited. It becomes clear from these overviews that different health problems and guidelines, and different health care settings, may need their own exploration of what would work to improve patient care. This is clearly shown in the 2 reviews of change interventions in this issue: one focusing on anxiety problems in primary and ambulatory (mental health) practice,8 the other on severe mental health problems both in in-hospital and in community settings.9 These are important papers from a new field of health services research (quality improvement research) that has become adult in recent years, for instance by the work of the Cochrane Center for Effective Practice and Organisation of Care. …