Background: Collaboration between physicians and pharmacists is one approach to address drug-related morbidity and achieve therapeutic goals. A collaborative practice of pharmaceutical care has been used in the Fairview Clinics System of Minneapolis-St Paul since 1999. Methods: The quality of therapeutic determinations made by pharmacists within this collaborative practice of pharmaceutical care was studied by a 12-member panel of physicians and pharmacists who used randomly selected patient records. This was a quality improvement and care process validation component of a study evaluating the effects of drug therapy management in patients receiving prepaid medical assistance. An implicit review process was used to evaluate the clinical credibility of therapeutic determinations made by pharmaceutical care practitioners. Results: A total of 5780 drug therapy problems were resolved for 2524 patients receiving pharmaceutical care. The rate of therapeutic goals achieved increased from 74% at the time of patients' initial pharmaceutical care encounters to 89% at patients' latest encounters. In this quality assessment analysis panel members performed a total of 4779 evaluations of clinical decisions. Panelists indicated agreement with the evaluations in 94.2% of cases, expressed a neutral opinion in 3.6% of cases, and disagreed in 2.2% of cases. Intraclass correlation coefficients ranged from 0.73 to 0.85. Conclusions: The decisions made by pharmaceutical care practitioners working in collaboration with physicians to provide drug therapy management services are clinically credible based on the evaluations and comments of a peer review panel. This study provides information on the quality of care provided by pharmacists when collaborating with physicians to provide drug therapy management services.