The potential of outpatient electronic health records (EHRs) to improve chronic disease outcomes has long been recognized, but rarely realized. Although prompts and reminders have been shown to increase test ordering and immunization rates, recent meta-analyses confirm the low impact of outpatient CDS systems on key intermediate outcomes of care such as glucose, blood pressure, or lipid control in adults with high cardiovascular risk. We first review the literature to identify key design and implementation features associated with CDS success. In the context of this literature, we provide a detailed description of the development, implementation, and maintenance of a series of Web-based EHR-linked outpatient CDS systems that (a) are currently used by 4 large medical groups with > 2 million patients, (b) are used at 70-80% of targeted visits, (c) have 95% primary care provider satisfaction rates, and (d) have significantly improved BP, glucose control, and cardiovascular risk in a series of NIH-funded randomized trials. We will also discuss the relative effectiveness of various training, incentive, and feedback strategies designed to promote sustained high CDS use rates. Workshop participants will be invited and encouraged to share their own experiences and insights as users and/or developers of clinical decision support systems in primary care. Of particular interest are insights on factors that either facilitate or impede design, implementation, and sustained use of successful primary care CDS systems.