Background: We describe the performance of an electronic health record (EHR)-linked, web-based primary care cardiovascular clinical decision support (CDS) system and the facilitators and barriers to dissemination. Methods: Algorithms identify patients at the point-of-care and target them to receive personalized and prioritized evidence-based treatment options. Printed versions of the CDS for patients and providers are used to elicit treatment preferences and facilitate shared decision-making. In 3 National Institutes of Health (NIH)-funded cluster-randomized trials, the CDS use ranged from 71%–77% of targeted patients, and clinicians reported 85%–98% satisfaction. Blood pressure control, glucose control, and 10-year cardiovascular risk trajectory significantly improved in patients cared for at clinics randomized to CDS vs usual care. Results: This CDS system has been disseminated to 4 large care delivery systems with about 2000 primary care clinicians in 4 states, with dissemination to an additional 60 safety-net clinics in 10 states underway. The CDS website currently evaluates 40,000 visits a day (9 million visits per year) with high reliability and 300 millisecond/case processing time. Facilitators of dissemination have included care system or payer interest in care improvement, clinician satisfaction, high CDS use rates with minimal impact on workflow, favorable effects on patient outcomes and shared decision-making, positive patient perceptions, standardization of care, and ability to rapidly translate new evidence/guidelines into practice. Barriers to dissemination include cost of implementation and lack of a corporate entity to market and manage ongoing support of the CDS system (not a strength of a research organization with limited ability or bandwidth to devote to this). Actual implementation costs per delivery system were about $100,000, mostly related to effort required for data mapping and programming the interconnectivity between EHR and the web service. Time required for implementation was about 4–6 months after data and service agreements were finalized and varied depending on perceived priority of the project and skill level of programmers at the recipient organization. Conclusion: This CDS system had high use rates, high primary care provider satisfaction, and significantly improved care in targeted adults and children. After 10 years of NIH-funded development and expansion, several potentially remediable factors limit widespread dissemination