Asthma is one of the most common chronic inflammatory disorders. Its prevalence varies worldwide between 5% and more than 20%. It isn’t clear why some people get asthma and others don’t, but it’s probably due to a combination of environmental and genetic factors. Asthma affects all ages: it is the most common chronic disease of childhood, adolescence and adulthood and has large effects on school and work performance of patients. Asthma is a serious challenge to public health. There is no cure and many patients remain uncontrolled despite available treatment. Combined efforts in public health, basic and clinical research are needed to fight this highly prevalent and increasing disease.