Abstract A project to define and test population-management roles in nursing was implemented in a large HMO. Three patient populations were selected: diabetics, patients with multiple sclerosis, and pregnant adolescents. Expert nurse clinicians in each of the three areas piloted the role for six months, including establishing a system of care coordination for the populations. In all three pilots, patient care outcomes were improved. Keys to success included aligning the work with the critical clinical work of the organization, practicing in multidisciplinary settings, and reporting objective outcome data to constituents.