OBJECTIVES: To determine effectiveness and costs of different guideline dissemination and implementation strategies.

DATA SOURCES: MEDLINE (1966 to 1998), HEALTHSTAR (1975 to 1998), Cochrane Controlled Trial Register (4th edn 1998), EMBASE (1980 to 1998), SIGLE (1980 to 1988), and the specialized register of the Cochrane Effective Practice and Organisation of Care group.

REVIEW METHODS: INCLUSION CRITERIA: Randomized‐controlled trials, controlled clinical trials, controlled before and after studies, and interrupted time series evaluating guideline dissemination and implementation strategies targeting medically qualified health care professionals that reported objective measures of provider behavior and/or patient outcome. Two reviewers independently abstracted data on the methodologic quality of the studies, characteristics of study setting, participants, targeted behaviors, and interventions. We derived single estimates of dichotomous process variables (e.g., proportion of patients receiving appropriate treatment) for each study comparison and reported the median and range of effect sizes observed by study group and other quality criteria.

RESULTS: We included 309 comparisons derived from 235 studies. The overall quality of the studies was poor. Seventy‐three percent of comparisons evaluated multifaceted interventions. Overall, the majority of comparisons (86.6%) observed improvements in care; for example, the median absolute improvement in performance across interventions ranged from 14.1% in 14 cluster‐randomized comparisons of reminders, 8.1% in 4 cluster‐randomized comparisons of dissemination of educational materials, 7.0% in 5 cluster‐randomized comparisons of audit and feedback, and 6.0% in 13 cluster‐randomized comparisons of multifaceted interventions involving educational outreach. We found no relationship between the number of components and the effects of multifaceted interventions. Only 29.4% of comparisons reported any economic data.

CONCLUSIONS: Current guideline dissemination and implementation strategies can lead to improvements in care within the context of rigorous evaluative studies. However, 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 quality improvement activities.