The effects of beta blocker therapy in the settings of heart failure and coronary artery disease have been well described, although little data exist in patients presenting with acute coronary syndromes undergoing percutaneous coronary intervention. The current study will attempt to evaluate the efficacy of beta blocker therapy in this setting. Pooled data from five randomized, controlled trials of abciximab during coronary intervention were used to analyze the clinical efficacy of beta blocker therapy. The pooled analysis evaluated the end points of all-cause mortality, myocardial infarction, repeat revascularization, and the combined endpoint of death and myocardial infarction in 2,894 patients. At 30 days, death occurred in 12 of 1,939 (0.6%) patients receiving beta blocker therapy and in 19 of 955 (2.0%) patients not receiving beta blocker therapy, (P < 0.001). At 6 months, death occurred in 33 of 1,939 (1.7%) patients receiving beta blocker therapy and 35 of 955 (3.7%) not receiving beta blocker therapy, (P < 0.001). After creating a propensity model and adjusting for variables predictive of mortality in the multivariable analysis, beta blocker therapy continued to be associated with a significant reduction in mortality. The findings were similar to those shown for the effects of beta blocker therapy in separate subgroups of patients with unstable angina and acute myocardial infarction. This analysis demonstrates a lower short-term mortality in patients receiving beta blocker therapy who undergo percutaneous coronary intervention for unstable angina or acute myocardial infarction.