OBJECTIVES This study investigated the association between copayment and adherence to statin treatment in a veteran population at the Veterans Affairs San Diego Healthcare System (VASDHS). METHODS This was a retrospective analysis of patients initiated on statin therapy and followed for 12 months to determine adherence. Patients who began a statin during the period of November 2006 to December 2007 were included. Patients who switched statin therapy or who were discontinued before 12 months were excluded. Eligibility was established if patients had at least two visits to their provider post-index date and one visit pre-index date. Adherence was defined as a medication possession ratio (MPR) ≥80%. Independent variables included: age, gender, ethnicity, BMI, number of medications, baseline lipid panel, percent service connection, and comorbid conditions. Service connection defines level of medical and prescription coverage benefit and awarded based on disability, socioeconomic and military-service factors. Non-parametric continuous data was evaluated using the Mann Whitney-U. Categorical data was evaluated using the Pearson Chi-squared test. Logistic regression model was used to determine predictors of adherence. RESULTS A majority of the cohort (N=6890) was 63.7 (±11.23) years old, male (95.6%), Caucasian (19.4%), taking simvastatin (84.6%), and had hypertension (73.0%). Statistically significant differences were seen in all variables between the adherent and nonadherent groups at baseline with few exceptions. Nonadherent patients had an MPR of 55% compared to adherent patients MPR of 95% (p<0.0005). No difference in adherence found between non-service connected patients and those service connected (p=0.449). Patients who were older (OR=1.01, 95%CI: 1.002-1.014), had higher percent service connection (OR=1.00, 95%CI: 1.000-1.004), and high quantity of medications (OR=1.05, 95%CI: 1.032-1.064) were more likely to be adherent. CONCLUSIONS Copayment had no affect on adherence. However, patients who had a higher percentage service connection were more likely to be adherent to their statin medication.