Asthma is a common disease in children. Current Swedish studies show a prevalence of 8-10 per cent at school age. Many infants and pre-schoolers have viral wheeze with asthma symptoms with colds. Viral wheeze is not linked to allergic sensitization or eczema. »True« asthma is characterized by eosinophilic airway inflammation, and allergic sensitization and eczema are frequent. The aim of asthma treatment is good symptom control, normal lung function and no, or minimal, side effects. Inhaled corticosteroids dramatically improved asthma treatment and are the mainstay of asthma treatment in all age groups. Today's treatment as a rule provides good asthma control and quality of life. The prognosis is good in viral wheeze. Most children grow out of their disease at age 2 to 3 years, although some not until school age. Many asthmatic children with allergy or eczema also improve when they grow older, although some later have a relapse of asthma.