Pharmacists can affect the delivery of primary care by addressing the challenges of medication therapy management. Most office visits involve medications for chronic conditions and require assessment of medication effectiveness, the cost of therapies, and patients' adherence with medication regimens. Pharmacists are often underused in conducting these activities. They perform comprehensive therapy reviews of prescribed and self-care medications, resolve medication-related problems, optimize complex regimens, design adherence programs, and recommend cost-effective therapies. Pharmacists should play key roles as team members in medical homes, and their potential to serve effectively in this role should be evaluated as part of medical home demonstration projects.