The authors sought to evaluate whether the level of systolic blood pressure (SBP) on hospital admission is an independent prognostic factor for in-hospital mortality of patients hospitalized with acute coronary syndrome (ACS). From October 2003 to September 2004, 2172 consecutive patients with ACS were included in the study (76% men). The in-hospital mortality rate was 3.2% in male and 5.7% in female patients (overall, 82 deaths; P=.009). An inverse association was observed between in-hospital mortality rate and levels of SBP (<100 mm Hg, death rate 17.8%; 100-120 mm Hg, 3.7%; 120-140 mm Hg, 2.9%; >140 mm Hg, 2.6%; P<.001). Women, hypertensives, diabetics, dyslipidemics, and older patients had higher levels of SBP compared with other groups. The SBP of patients who received thrombolytic agents was lower than that of those who did not receive this therapy. Multi-adjusted analysis revealed that a 10-mm Hg increment in SBP was associated with a 27% lower likelihood of death during hospitalization (odds ratio, 0.73; 95% confidence interval, 0.66-0.90).