Healthcare organizations seeking to improve clinical practices often have disappointing results because the planned innovations are not successfully implemented. To increase the understanding of implementation, we analyzed the national spread of an ambulatory innovation in the Department of Veterans Affairs. This study provides support for a conceptual model that posits that the extent to which a clinical innovation is implemented will be affected by factors in 3 domains: (1) intentional activities to introduce, spread, and support the innovation; (2) the attitudes and capabilities of clinic staff responsible for implementing the innovation; and (3) the context of the facility in which the innovation is being introduced. Among the strongest predictors of successful implementation, management support for the innovation and clinic team knowledge and skills to make changes successfully were significant across both primary care and specialty clinics.