OBJECTIVES: The objective of the study is to identify and measure the extent to which gender differences in Angiotensin II Converting Enzyme Inhibitors (ACEI) and Angiotensin Receptor Blockers (ARB) prescriptions could be explained by demographic, socio-economic and health status factors. METHODS: Secondary data analyses of merged Veteran Health Administration (VHA) and Medicare claims data for the fiscal years 1997 through 2000. Diabetes was identified with International Classification of Diseases, 9th edition (ICD-9-CM) codes from inpatient or outpatient physician visits over the 24 month period. The independent variables were demographics, socio-economic characteristics, physical health and mental health conditions. Based on the parameter estimates and distribution of individual characteristics, we performed traditional and extended decomposition techniques to analyze the drivers behind the gender differences in lipid control. Population Studied: The final study sample consisted of 263,730 veterans who had an index creatinine value in FY1999, and qualifying creatinine value between 90 and 365 days following. There were 5,458 women and 258,272 men veterans. RESULTS: Overall, more men (58.1%) than women (51.3%) were prescribed ACEI/ARBs. Even after controlling for many observable characteristics, women were less likely to have ACEI/ARB prescriptions. The adjusted odds ratio was 0.82 with 95% CI = 0.77, 0.87. . Nearly one third of the 7 percentage point gap in prescription drug use was explained by variables included in the model. The gender gap in ACEI/ARBs could be explained by differences in indications for ACEI/ARB, diabetes severity, and mental illness (depression, anxiety, and PTSD). CONCLUSIONS: Gender differences in ACEI/ARB exist and only about one-third of the difference could be explained by differences in patient characteristics. Mental health conditions may be a barrier to lower ACEI/ARB rates among women. Our findings highlight the importance of population health approach to medication use in terms of coordinated care for mental illness and physical illnesses.