The effectiveness and efficiency of guideline dissemination and implementation strategies were systematically reviewed to assess the impact of various strategies on clinical practice. The study aimed to evaluate the effectiveness and costs of different strategies for developing, disseminating, and implementing clinical guidelines, estimate the resource implications of these strategies, and develop a framework for deciding when it is efficient to develop and introduce clinical guidelines. A comprehensive search of multiple databases, including MEDLINE, Healthstar, Cochrane Controlled Trial Register, EMBASE, SIGLE, and the Cochrane Effective Practice and Organisation of Care (EPOC) group's specialized register, was conducted. The search strategy was designed to identify rigorous evaluations of the introduction of clinical guidelines into medical practice. The study included a wide range of study designs, including randomized controlled trials (RCTs), controlled clinical trials (CCTs), controlled before and after (CBA) studies, and interrupted time series (ITS) designs. The study found that 235 studies reporting 309 comparisons met the inclusion criteria. Of these, 73% evaluated multifaceted interventions, although the maximum number of replications of a specific multifaceted intervention was 11 comparisons. Overall, the majority of comparisons reporting dichotomous process data observed improvements in care, although there was considerable variation in the observed effects both within and across interventions. Commonly evaluated single interventions included reminders, dissemination of educational materials, and audit and feedback. Multifaceted interventions involving educational outreach were also evaluated, with the majority of interventions observing modest to moderate improvements in care. The study also explored the economic implications of these strategies. Only 29.4% of comparisons reported any economic data, with most studies only reporting costs of treatment. Only 25 studies reported data on the costs of guideline development or dissemination and implementation. The majority of studies used process measures for their primary endpoint, despite the fact that only three guidelines were explicitly evidence-based. The study concluded that there is an imperfect evidence base to support decisions about which guideline dissemination and implementation strategies are likely to be efficient under different circumstances. Decision makers need to use considerable judgment about how best to use the limited resources they have for clinical governance and related activities to maximise population benefits. They need to consider the potential clinical areas for clinical effectiveness activities, the likely benefits and costs required to introduce guidelines, and the likely benefits and costs as a result of any changes in provider behaviour. Further research is required to develop and validate a coherent theoretical framework of health professional and organisational behaviour and behaviour change to inform better the choice of interventions in research and service settings, and to estimate the efficiency of dissemination and implementation strategies in the presence of different barriers and effect modifiers.The effectiveness and efficiency of guideline dissemination and implementation strategies were systematically reviewed to assess the impact of various strategies on clinical practice. The study aimed to evaluate the effectiveness and costs of different strategies for developing, disseminating, and implementing clinical guidelines, estimate the resource implications of these strategies, and develop a framework for deciding when it is efficient to develop and introduce clinical guidelines. A comprehensive search of multiple databases, including MEDLINE, Healthstar, Cochrane Controlled Trial Register, EMBASE, SIGLE, and the Cochrane Effective Practice and Organisation of Care (EPOC) group's specialized register, was conducted. The search strategy was designed to identify rigorous evaluations of the introduction of clinical guidelines into medical practice. The study included a wide range of study designs, including randomized controlled trials (RCTs), controlled clinical trials (CCTs), controlled before and after (CBA) studies, and interrupted time series (ITS) designs. The study found that 235 studies reporting 309 comparisons met the inclusion criteria. Of these, 73% evaluated multifaceted interventions, although the maximum number of replications of a specific multifaceted intervention was 11 comparisons. Overall, the majority of comparisons reporting dichotomous process data observed improvements in care, although there was considerable variation in the observed effects both within and across interventions. Commonly evaluated single interventions included reminders, dissemination of educational materials, and audit and feedback. Multifaceted interventions involving educational outreach were also evaluated, with the majority of interventions observing modest to moderate improvements in care. The study also explored the economic implications of these strategies. Only 29.4% of comparisons reported any economic data, with most studies only reporting costs of treatment. Only 25 studies reported data on the costs of guideline development or dissemination and implementation. The majority of studies used process measures for their primary endpoint, despite the fact that only three guidelines were explicitly evidence-based. The study concluded that there is an imperfect evidence base to support decisions about which guideline dissemination and implementation strategies are likely to be efficient under different circumstances. Decision makers need to use considerable judgment about how best to use the limited resources they have for clinical governance and related activities to maximise population benefits. They need to consider the potential clinical areas for clinical effectiveness activities, the likely benefits and costs required to introduce guidelines, and the likely benefits and costs as a result of any changes in provider behaviour. Further research is required to develop and validate a coherent theoretical framework of health professional and organisational behaviour and behaviour change to inform better the choice of interventions in research and service settings, and to estimate the efficiency of dissemination and implementation strategies in the presence of different barriers and effect modifiers.