An acute exacerbation of chronic bronchitis represents one of the most common illnesses treated by physicians. In spite of this, the role of infection in general, and bacterial infection in particular, is difficult to establish. Clinical signs and symptoms in patients with bacterially associated disease are not separable from those in patients without bacterial infection. Studies evaluating the efficacy of antibiotics in this setting, though suggesting that antibiotics are useful, do not provide sufficient benefit to justify routine antibiotic use. Further, these studies have not defined a subpopulation for whom antibiotics are necessary. Routine antibiotic use may delay diagnosis of other serious disease and is unequivocally very expensive, primarily because of the use of the newer and higher-cost drugs. In some situations, such as severe infection or associated with surgery, routine antibiotic use may be justified, but the use of sputum culture to guide antibiotic choice is recommended. A well designed study to finally settle the issue of antibiotic need in acute exacerbations of chronic bronchitis is badly needed.