PURPOSE: Although clinical-practice guidelines (CPGs) are implemented on the assumption that they will improve the quality, efficiency, and consistency of health care, they generally have limited effect in changing physicians' behavior. The purpose of this study was to design and implement an effective program for formulating, promulgating, and implementing CPGs to foster the development of an evidence-based culture in an Israeli HMO. METHOD: The authors implemented a four-stage program of stepwise collaborative efforts with academic institutions composed of developing quantitative tools to evaluate prescribing patterns, updating CPGs, collecting MDs' input via focus groups and quantitative surveys, and conducting a randomized controlled trial of a two-stage, multipronged intervention. The test case for this study was the development, dissemination, and implementation of CPG for the treatment of acute uncomplicated cystitis in adult women. Interventions in the form of a lecture at a conference and a letter with personalized feedback were implemented, both individually and combined, to improve physicians' rates of prescribing the first-line drug, nitrofurantoin, and, in the absence of nitrofurantoin, adhering to the recommended duration of three days of treatment with ofloxacin. RESULTS: The tools and data-generating capabilities designed and constructed in Stage I of the project were integral components of all subsequent stages of the program. Personalized feedback alone was sufficient to improve the rate of adherence to the guidelines by 19.4% (95% CI = 16.7, 22.1). CONCLUSIONS: This study provides a template for introducing the component of experimentation essential for cultivating an evidence-based culture. This process, composed of collaborative efforts between academic institutions and a managed care organization, may be beneficial to other health care systems.