Preventable hospital admissions and readmissions are indicators of health system fragmentation associated with suboptimal patient outcomes and avoidable costs of care. Three case studies illustrate the potential of care management programs to address this problem by improving care coordination and transitions among high-risk patients. Study sites included two academic medical centers and a managed care organization owned by a home health agency. The sites employed bundles of interventions involving multidisciplinary teams to improve provider communication, patient and family education, care transitions from the hospital, and follow-up ambulatory care. Results include a lengthening in average time between hospital encounters among asthmatic children and relative reductions in 30-day readmission rates of 46 percent among elderly patients with heart failure and of 21 percent among dually eligible Medicare and Medicaid beneficiaries with special needs. Spreading such models will likely require supportive changes in payment policy or aligned incentives between payers and providers.