OBJECTIVES: 1) To evaluate adherence to chronic disease (Diabetes, Hypertension, and Hyperlipidemia) medications of patients enrolled in an employer sponsored Medication Therapy Management (MTM) program. 2) To determine the effect of adherence on the clinical outcomes of patients with diabetes and hypertension in the MTM program. METHODS: This was a retrospective, longitudinal study. Adherence data was obtained from an independent pharmacy participating in an employer sponsored MTM program  in the form of pharmacy refill records for 272 patients. Clinical data was obtained through patient chart reviews. Medication adherence was calculated using Medication Possession Ratio (MPR) and weighted average adherence was calculated for each class of medications. Pearson correlation was used to determine the relationship between medication adherence and desired clinical outcomes-HbA1c for diabetic patients and mean arterial pressure for hypertension patients. Multiple linear regression was used to determine if medication adherence was a predictor of clinical outcomes. Data analysis was performed using SPSS version16.0 and Microsoft Excel. RESULTS: Pearson correlation results indicated that MPR to diabetic medications was significantly correlated with age (r=0.387, p=0.000) and gender (r=-0.167, p=0.021). Further, age was significantly correlated with number of diseases (r=0.278, p=0.000) among diabetic patients. However, there were no significant predictors of change in A1c among diabetic patients. Among hypertension patients, change in mean arterial pressure was significantly correlated with gender (r=0.123 p=0.037) and MPR (r=-0.146, p=0.013). MPR was also found to be significantly correlated with gender (r=-0.148, p=0.012, co-pay (r=0.142, p=0.016), and number of diseases (r=0.142, p=0.016).  Regression model for hypertension patients indicated that MPR (β = -0.136, p = 0.024) was a significant predictor of change in mean arterial pressure. CONCLUSIONS: Patients enrolled in an employer sponsored MTM program showed high weighted average adherence to most of the classes of diabetes, hypertension, and hyperlipidemia medications. This study also identified predictors of clinical outcomes associated with diabetes and hypertension.