Congestive heart failure is a condition in which the heart muscle cannot pump blood normally, leading to such symptoms as shortness of breath and fluid accumulation. Heart failure is a common and serious illness in the United States, particularly in older adults. Although many medicines improve symptoms and survival in heart failure, patients with this condition often do not do well, and better treatments are needed. β-Blockers are drugs that slow the heart rate, lower blood pressure, decrease the strength of heart muscle contraction, and prevent abnormal heart rhythms. Some studies have suggested that β-blockers may help patients with heart failure, but the likelihood that they are helpful is unclear.