Anemia has been shown to predict adverse events in patients presenting with acute coronary syndromes and non-ST-elevation myocardial infarctions (MIs). Less is known about the value of blood transfusions in this setting. We sought to evaluate the impact of red blood cell transfusions on outcomes. Transfusion in anemic patients admitted with suspected acute coronary syndrome/non-ST-elevation MIs led to a significant increase in 30-day recurrent MI or death (odds ratio 3.05, 95% confidence interval 1.80 to 5.17, p <0.001). This relation persisted after adjusting for significant univariate predictors: hypotension on presentation, pulmonary edema, and increased troponin-I levels (odds ratio 2.57, 95% confidence interval 1.41 to 4.69, p <0.001). In conclusion, the risk versus benefit of transfusion in patients presenting with an acute coronary syndrome needs careful assessment.