The Action to Control Cardiovascular Disease in Diabetes (ACCORD) blood pressure trial is an unmasked, open-label, randomized trial with a sample size of 4,733 participants. This report describes the rationale, design, and methods of the blood pressure interventions in ACCORD. Participants eligible for the blood pressure trial are randomized to 1 of 2 groups with different treatment goals: systolic blood pressure <120 mm Hg for the more intensive goal and systolic blood pressure <140 mm Hg for the less intensive goal. The primary outcome measure for the trial is the first occurrence of a major cardiovascular disease (CVD) event, specifically nonfatal myocardial infarction or stroke, or cardiovascular death during a follow-up period ranging from 4-8 years. The ACCORD blood pressure trial should provide the first definitive clinical trial data on the possible benefit of treating to a more aggressive systolic blood pressure goal in reducing CVD events in patients with diabetes mellitus.