Chronic bronchitis (CB) is a common feature associated with cigarette smoking. When airflow obstruction is present, this disorder is called chronic obstructive pulmonary disease (COPD). The exact prevalence of CB in COPD is unknown, but is thought to affect approximately 30 to 40% of patients and its prevalence increases with disease severity. Although earlier studies did not show a relationship between CB and COPD incidence, subsequent studies suggest that CB may represent an early marker of susceptibility to the effects of cigarette smoking and identify a subgroup of patients with a high risk of developing COPD. In addition, there has been an increased understanding that CB is not just an innocent disorder and when present in COPD can predict worsening functional status and, possibly, increased morbidity and mortality.