Bordetella pertussis is a highly contagious bacterium known to cause pertussis (whooping cough) and is transmitted via airborne droplets. Although childhood vaccination has dramatically reduced reported pertussis cases, the incidence of the disease has increased over the past 20 years, most notably in previously immunized adolescents and adults. Pertussis should be suspected in patients of all ages with cough who meet the clinical criteria for the disease. Diagnostic tests currently approved by the U.S. Food and Drug Administration for pertussis infection have low sensitivity. Regardless of test results, physicians should treat clinically suspected pertussis with antimicrobials and report cases to their state health department. A 14-day erythromycin regimen has been the treatment of choice; however, shorter-course macrolide antibiotics (e.g., azithromycin, clarithromycin) may be as effective with fewer adverse effects and better adherence to therapy. The recently recommended tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccine for adolescents and adults may decrease the incidence of pertussis in infants--the group at the greatest risk of pertussis complications.