While pharmacists have long been delivering personalized clinical patient services, recognition of pharmacists as health care providers, realization of the value of pharmacist cognitive services, and fair payment for pharmacists have been slow to evolve. This article tracks the evolution of medication therapy management (MTM) services provided by pharmacists, using the Medicare Modernization Act of 2003 as a springboard. The core elements of MTM services are discussed and reviewed, and MTM programs and services as outlined in the Medicare Part D outpatient prescription drug benefit are thoroughly examined. Pharmacist and patient perceptions of the value of MTM are outlined, and barriers to MTM implementation at the pharmacy/pharmacist level are evaluated. Key studies showing the economic and clinical benefits of MTM services are discussed, as well as important drivers that may propel MTM beyond the Medicare Part D threshold.