OBJECTIVES: To describe the association between the three-year average glycosylated hemoglobin (A1C) and cardiovascular outcomes in adults with type 2 diabetes mellitus (T2DM). METHODS: In this nested case-control study, 245,346 adults (≥ 18 years) with T2DM were identified among members of Kaiser Permanente Southern California.  Type 2 diabetic patients had at least two ICD-9 diagnosis codes for T2DM (250.x0, 250.x2) and either A1C > 7.5% or prescriptions for hypoglycemic agents from 2002-2007.  Using hospital records and death certificates, cases were defined as patients with a nonfatal MI, nonfatal stroke, or death due to cardiovascular (CV) causes (MI, stroke, heart failure, arrhythmia, sudden cardiac death) in the period 2005-2007.  Four controls from the T2DM pool were matched to each case based on age, sex and index date (date of the case defining event).  A conditional logistic regression model was used to estimate the odds-ratio (OR) of cardiovascular events comparing patients with an average A1C ≤ 6 % and those with average A1C >8% to patients with average A1C between 6-8%, considered ‘near A1C target’.  A1C categories were assigned to each patient based on average A1C over the three years prior to the index date.  RESULTS: A total of 44,628 controls were matched to 11,157 cases.  After adjusting for CV related medications, comorbidities, and other confounders, patients with an average A1C ≤6% were 50% more likely to experience a CV event than the ‘near A1C target’ T2DM patients (OR = 1.50, 95% CI 1.33 – 1.69, p<0.0001).  Patients with an average A1C > 8% experienced a 14% increase in odds of a CV event (OR = 1.14, 95% CI 1.03-1.26, p=0.01). CONCLUSIONS: Compared to those with mean A1C levels between 6-8%, patients with T2DM who achieved mean A1C levels of ≤6% or failed to decrease their A1C below 8% over a 3-year period are at increased risk for cardiovascular events.