The use of helium in medicine was first described by Barach who treated obstructive lesions of the airways, in 1936. Since then, only scattered reports can be found in the medical literature until the 80s, when interest in helium resurged for the treatment of acute asthma, as deaths from this disease begun to rise. At least theoretically, because of its physical properties, helium should be useful in several obstructive conditions of the airways including upper airway obstruction, croup, post-extubation stridor, asthma attacks, exacerbations of chronic obstructive pulmonary disease (COPD), etc. However, there is not enough evidence to support the systematic use of heliox to treat severe stages or acute exacerbations of COPD in either ventilated or non ventilated patients because there is currently no convincing impact on patient outcome. Therefore, at present, widespread use of heliox cannot be recommended in clinical practice.