Measure Accurately, Act Rapidly, and Partner With Patients (MAP) is an evidence-based protocol implemented to improve hypertension control in a clinic for underserved patients (49.9% Medicaid and 50.2% black). Patients with hypertension seen during the year before intervention and with at least one visit during the 6-month intervention (N = 714) were included. If initial attended blood pressure (BP; standard aneroid manometer) was ≥140/≥90 mm Hg, unattended automated office BP was measured in triplicate and averaged (Measure Accurately) using an Omron HEM-907XL. When automated office BP was ≥140/≥90 mm Hg, Act Rapidly included intensification of antihypertensive medications, assessed by therapeutic inertia. Partner With Patients included BP self-monitoring, reducing pill burden, and minimizing medication costs, which was assessed by systolic BP change per therapeutic intensification. Between baseline and the last study visit, BP control to <140/<90 mm Hg increased from 61.2% to 89.9% (P <.0001). MAP rapidly and significantly improved hypertension control in medically underserved patients, largely as a result of measuring BP accurately and partnering with patients.