The phenotype is the result of the observable characteristics of a subject resulting from the interactions between a genotype and its environment. Phenotyping asthmatic patients is a current search to better capture the heterogeneity of this disease with potential overlaps with other chronic bronchial disease such as COPD. This aspect is crucial in severe asthma where important unmet needs are found. The criteria used to phenotype asthma are issued from current clinical, functional and pathophysiological findings. The defined phenotypes will take benefit from more focused therapeutical avenues.