While the patient safety field originated in studies of error in hospitals, safety in ambulatory care remains relatively less studied. Even within ambulatory safety, few studies address safety issues in chronic disease management, despite the fact that most medical care is provided in this context. In this article, the authors use evidence and case vignettes to develop a conceptual model of ambulatory safety and discuss how this model differs from the classic Donabedian triad. The framework emphasizes the role of health systems (including care coordination and information technology) and patient factors (such as health literacy) as determinants of safety and health outcomes.