OBJECTIVES To determine if differences existed between the intervention group [after participating in a pharmacist-provided telephone medication therapy management (PPMTM) program] and the control group in: 1) Medication/health-related problems (MHRPs); 2) Medication adherence; and 3) Total Part D drug costs. METHODS This quasi-experimental study of Part D beneficiaries from a Texas health plan used the Andersen Model as its theoretical framework. Predisposing factors were age, gender, and race; need factors were number of medications, number of chronic diseases and medication regimen complexity. The intervention and control groups were matched on number of medications and number of chronic diseases. The health behavior was PPMTM participation. Outcomes were changes in: 1) Number of MHRPs; 2) Medication adherence using medication possession ratio (MPR); and 3) Total drug costs. Multivariate regression was used for group comparisons of outcomes. RESULTS The intervention (n = 60) and control (n = 60) groups were not statistically different in predisposing or need factors except for gender (intervention = 51.7% male; control = 28.3% male; p=0.009). At baseline, 4.8 (± 2.7) MHRPs were identified in the intervention group and 9.2 (± 2.9) in the control group. At the 6-month follow-up, 2.5 (± 2.0) and 7.9 (± 3.0) MHRPs remained, respectively. Multivariate regression revealed that the intervention group had significantly more MHRPs resolved (p=0.0003) when compared to the control group, while controlling for predisposing and need factors. There were no other significant predictors of MHRP resolution, Analyses showed no significant predictors of change in MPR or total drug costs from baseline to 6-month follow-up. CONCLUSIONS A telephone MTM program was effective in resolving MHRPs among Medicare beneficiaries; however, no significant differences existed between the intervention and control groups in medication adherence and total drug costs.