BACKGROUND: Mail order pharmacies are commonly used to deliver CVD risk factor medications. Previous studies have shown that mail order pharmacy use is associated with greater medication adherence; however, no studies have examined whether mail order pharmacy use is related to improved CVD risk factor outcomes. OBJECTIVE: To examine the comparative effectiveness of mail order pharmacy vs. local pharmacy use on LDL-C control in new statin users. DESIGN: Observational cohort study. PATIENTS: 100,298 adult Kaiser Permanente Northern California (KPNC) members who were new users of statins between January 1, 2005 and December 31, 2007. MEASUREMENTS: The main outcome measure was LDL-C control in the 3-15 month period after statin therapy was initiated. RESULTS: After adjustment for patient, clinical, and census-block characteristics, and for potential unmeasured differences between mail order and local KPNC pharmacy users with instrumental variables analysis, 85.0% of patients who used the mail order pharmacy to deliver their statin at any time achieved target LDL-C levels compared with 74.2% of patients who only used the local KPNC pharmacy to dispense the statin (p < 0.001). Greater adjusted rates of LDL-C control in mail order pharmacy users were seen across all gender and race/ethnicity subgroups. CONCLUSIONS: Mail order pharmacy use was positively associated with LDL-C control in new statin users. Future research should continue to explore the relationship between mail order pharmacy use and outcomes, and address how to appropriately target mail order services to patients most likely to benefit without compromising patient choice, care, and safety.