Beta-adrenergic blocking agents, or beta-blockers, are indicated in the management of angina pectoris, myocardial infarction, hypertension, congestive heart failure (CHF), cardiac arrhythmias, and thyrotoxicosis, and are given to reduce perioperative complications. Despite clear evidence that they reduce morbidity and mortality, clinicians are often hesitant to administer them for fear of adverse reactions. Over the past several years, many of the contraindications traditionally listed for betablockers have been questioned and disproved. Beta-blockers were contraindicated in CHF because of their intrinsic negative inotropic activity, but have now been shown to be beneficial, partly due to their ability to enhance sensitivity to sympathetic stimulation. Beta-blockers have also been contraindicated for patients with obstructive lung diseases, such as asthma and chronic obstructive pulmonary disease, due to the potential risk for bronchospasm. However, new evidence has shown that cardioselective beta-blockers are safe in patients with obstructive lung diseases, and may actually be beneficial by enhancing sensitivity to endogenous or exogenous beta-adrenergic stimulation. This article will review the evidence concerning the safety of beta-blocker use in patients with CHF and concomitant obstructive lung disease, with specific attention to tracking the transition from myth to evidence- based practice.