OBJECTIVES: The objectives of this study were to: 1) assess the quality of patient care provided by 6 Medication Therapy Management (MTM) pharmacists who were working collaboratively with physicians in 6 ambulatory care clinics in the Minneapolis, MN metropolitan area; and 2) determine the MTM pharmacists’ ability to identify and resolve drug therapy problems. METHODS: The quality of therapeutic determinations made by pharmacists within this collaborative practice of MTM was studied using a 9-member panel of physicians (6) and pharmacists (3). The panel reviewed the care provided to nine randomly selected patient records from the 286 MTM patients who were Blue Cross/Blue Shield Blue Plus members. A structured implicit review process was used by the reviewers to specify their level of agreement with the therapeutic decisions made by the MTM pharmacists. The reviewers used a 7-point Likert scale to specify their level of agreement with each therapeutic decision. RESULTS: There were 6444 therapeutic review determinations made by the review panel. The 9 reviewers expressed agreement with 90.7% of the decisions. They expressed disagreement with only 2.8% of the decisions. For each therapeutic decision, two-thirds or more of the reviewers agreed with the decision made in 99.9% of the cases. There was no difference in the mean ratings of the 9 patients based on an ANOVA (p=0.906). Regarding drug therapy problems (DTP's), there were 20 DTP's identified during the initial patient visits. All but 5 DTP's were resolved by the second visit. CONCLUSIONS: The decisions made by MTM practitioners working in collaboration with physicians are clinically credible based on the ratings and comments of a peer review panel. This study provides information on the quality of care provided by pharmacists in the collaborative practice of medication therapy management.