Objective: To estimate the proportion of a population underutilizing previously initiated therapy with statins and/or angiotensin converting enzyme inhibitors or angiotensin-II receptor blockers (ACEi/A2RB) and, of these, percent with high cardiovascular risk and how well they are identified by a strategy that targets new users. Methods: The study sample consists of a geographically defined subset of a commercially insured population who were age 25 to 84 on October 31, 2007 and continuously enrolled from January 2002 through November 2007. For all patients with any history of filling a prescription in the respective drug category January 2002 to June 2006, the proportion of days covered (PDC) July 2006 to June 2007 is deduced from dispensed dates and days supplied. Underutilization is defined as PDC 0% or >0%- <80%. Claims January 2002 - June 2006 are assessed for high cardiovascular risk criteria including: acute myocardial infarction, coronary revascularization, coronary atherosclerosis, acute ischemic stroke, diabetes, peripheral arterial disease, abdominal aortic aneurysm, nitrates, platelet aggregation inhibitors, diabetes therapy, cilastazol or pentoxyphylline. Results: Of 294,734 in the sample, 70,814 (24.0%) filled >= 1 prescription for a statin and 65361 (22.2%) for an ACEi/A2RB between 2002 and June 2006. During the subsequent 12 months, PDC was 0% and >0-<80%, respectively, for: 19.1% and 34.5% of all patients with previous statin history, 16.2% and 33.1% of those satisfying risk criteria; 26.7% and 26.7% of all with previous ACEi/A2RB history, 25.6% and 26.7% of those satisfying risk criteria. Patients who were new users in preceding 12 months (July 2005 – June 2006) comprised 10.9% of high risk patients underutilizing previously started statin therapy and 7.6% of those underutilizing previously started ACEi/A2RB therapy. Conclusion: Underutilization of cardiovascular risk-lowering medications is an important problem that requires strategies beyond targeting new users.