Chronic obstructive pulmonary disease (COPD) is a leading cause of death, and constitutes a major medical and an increasing economic problem for acute and long term care. A low level of irreversible airway obstruction when in stable condition, hypercapnia, hypoxia, the presence of comorbid heart disease, right ventricular failure, and low serum albumin are the main factors related to risk of exacerbations. Bronchial infections, bronchospasm, left ventricular failure, pneumonia, pneumothorax and thromboembolism are described as the most frequent relapsing causes of COPD. During exacerbation, the inflammatory process, the ventilation/perfusion (V'A/Q') mismatching, an increased airflow resistance and dynamic hyperinflation (PEEPidyn) expose the respiratory muscles to the risk of fatigue, eventually leading to ventilatory pump failure and rising hypercapnia. Prevention of exacerbations and subsequent hospitalisations may be obtained with careful rehabilitation programs, a strict drug protocol, long term oxygen therapy and sometimes using home noninvasive mechanical ventilation (NMV). During exacerbation proper management of infection and lung mechanics derangement has to be adopted using an accurate assessment of severity and standardized treatment protocols. Patient history and examination and functional tests are beneficial to decide how and where to treat these patients. Mechanical ventilation (possibly noninvasive) may be required to reverse the acute episode. The aims of all these procedures remain: i) to prolong length and quality of life; ii) to save costs. Both hospital and post-discharge mortality of exacerbated COPD remain high while quality of life appears to be poor. Future studies will elucidate the relation between number and severity of exacerbations and prognosis.