Severe asthma and difficult-to-treat asthma are major issues in public health, given the mortality and morbidity they induce and their detrimental effects on patients' quality of life. The economic consequences should not be overlooked either. Published studies suggest that asthma-related medical resource use increases with the degree of asthma severity. Medical resource use incurred by severe (and/or difficult-to-treat) asthma could be reduced in part by more appropriate treatment, better patient education, improved coordination of disease management and treatment of comorbid diagnoses. The specific difficulties in the management of severe asthma and/or difficult-to-treat asthma must nonetheless be kept in mind. Recent new treatments appear promising, but their costs and indications in actual medical practice require better definition.