Disease management programs based on the Chronic Care Model are expected to improve the quality of chronic care delivery. However, evidence to date for such improvement and how it is achieved is scarce. In 2010 and again in 2011, we surveyed professionals in twenty-two primary care practices in the Netherlands that had implemented the Chronic Care Model of disease management beginning in 2009. The responses showed that, over time, chronic illness care delivery improved to advanced levels. The gains were attributed primarily to improved relational coordination-that is, raising the quality of communication and task integration among professionals from diverse disciplines who share common objectives. These findings may have implications for other disease management efforts by collaborative care teams, in that they suggest that diverse health care professionals must be strongly connected to provide effective, holistic care.