Chronic obstructive pulmonary disease (COPD) is an increasingly important health problem world-wide. Whereas most other leading diseases have shown a decline in the past decades, COPD morbidity and mortality is on a steady increase. Exacerbations are usually defined as an increase in cough, a change in the colour or quantity of sputum, and a worsening dyspnea. The role of bacterial infections and the efficacy of antimicrobial therapy in acute exacerbations of chronic bronchitis (AECD) is still controversial. Exacerbations of chronic bronchitis are a common occurrence in clinical practice and are a leading cause of antibiotic prescription among respiratory infections. It is still uncertain whether each new exacerbation may deteriorate the natural history of chronic bronchitis. Undoubtedly, every episode includes a temporary worsening in lung function and may therefore pose the threat of respiratory failure or death in more severely obstructed patients.Allegra, L. is the author of 'Mechanisms and Management of Copd Exacerbations' with ISBN 9788847000667 and ISBN 8847000661.