Boxed warnings, commonly referred to as "black box" warnings, are issued by the U.S. Food and Drug Administration and featured in the labeling of drugs associated with serious adverse reactions. These safety concerns are typically identified through the Adverse Event Reporting System and the Office of Surveillance and Epidemiology, which evaluates postmarket safety findings. The most common type of warning is issued when there is a potentially serious adverse effect that must be carefully weighed against the potential benefit of the drug. Warnings are also issued to draw attention to dosing, monitoring requirements, and potential drug interactions. Boxed warnings have been issued recently for oral sodium phosphate bowel preparations, fluoroquinolone antibiotics, and salmeterol. Despite these highly publicized warnings, all of these medications remain viable treatment options with appropriate patient selection. Ultimately, physicians must decide whether to prescribe drugs with boxed warnings. (Am Fam Physician. 2010;81(3):298-303, 304. Copyright (C) 2010 American Academy of Family Physicians.)