To evaluate the potential for a patient-centered medical home initiative to reduce utilization and cost while improving quality, we examined a natural experiment involving 11 primary care practices in Cincinnati, Ohio, that participated in the Aligning Forces for Quality Multi-Payer Patient Centered Medical Home pilot. Our research design involved difference-in-difference analyses, comparing changes in utilization, costs, and quality between patients attributed to pilot practices compared with those attributed to a matched comparison cohort after 2 years of active engagement by the practices. The Cincinnati pilot was associated with a reduction of ambulatory care–sensitive emergency department visits of approximately 0.7 per 1,000 member months or approximately 22.6% (p = .01). While there was a reduction in total costs of care of $7,679 per 1,000 member months, the difference did not reach statistical significance. After 2 years of the pilot, lipid testing in diabetics had increased by 2.7 percentage points (a 3.3% improvement; p < .0001). Patient-centered medical homes have the potential to improve the quality of care and reduce emergency department use but expectations for cost control in a relatively short time horizon and absent other changes may be unrealistic.