CONTEXT: High resting blood pressure (BP) is among the best studied and established risk factors for cardiovascular disease. However, little is known about the relationship between BP under acute stress, such as in acute chest pain, and subsequent mortality. OBJECTIVE: To study long-term mortality related to supine BP in patients admitted to the medical intensive care unit (ICU) for acute chest pain. DESIGN, SETTING, AND PARTICIPANTS: Data from the RIKS-HIA (Registry of Information and Knowledge About Swedish Heart Intensive Care Admissions) was used to analyze the mortality in relation to supine admission systolic BP in 119,151 participants who were treated at the ICU for the symptom of chest pain from 1997 through 2007. Results from this prospective cohort study were presented according to systolic BP quartiles: Q1, less than 128 mm Hg; Q2, from 128 to 144 mm Hg; Q3, from 145 to 162 mm Hg; and Q4, at or above 163 mm Hg. MAIN OUTCOME MEASURE: Total mortality. RESULTS: Mean (SD) follow-up time was 2.47 (1.5) years (range, 1-10 years). One-year mortality rate by Cox proportional hazard model (adjusted for age, sex, smoking, diastolic BP, use of antihypertensive medication at admission and discharge, and use of lipid-lowering and antiplatelet medication at discharge) showed that participants in Q4 had the best prognosis (hazard ratio [HR], 0.76; 95% confidence interval [CI], 0.72-0.80, Q4 compared with Q2; corresponding risks for Q1 were HR, 1.46; 95% CI, 1.39-1.52, and for Q3, HR, 0.83; 95% CI, 0.79-0.87). Patients in Q4 had a 21.7% lower absolute risk compared with Q2, patients in Q3 had a 15.2% lower risk than in Q2, and patients in Q1 had a 40.3% higher risk for mortality than in Q2. The worse prognosis in Q2 compared with Q4 was independent of body mass index and previous diagnoses and similar when analysis was restricted to patients with a final diagnosis of angina or myocardial infarction (HR, 0.75; 95% CI, 0.71-0.80, Q4 compared with Q2). CONCLUSION: Among patients admitted to the ICU for chest pain, there is an inverse association between admission supine systolic BP and 1-year mortality rate.