The prevalence of asthma in children continues to increase in many parts of the world, with the highest increases in industrialized urban societies. Although the exact cause of the increase remains undefined the "hygiene hypothesis" where lower exposures to infectious agents that stimulate the production of Th1 lymphocytes thus allowing proliferation of Th2 lymphocytes that mediate allergic diseases has gained popularity. Asthma is an inflammatory disorder of the airways mediated by eosinophils and Th2 cytokines. Thus far, efforts at primary prevention have fallen short and therapy is targeted at preventing symptoms, morbidity and mortality and improving the patients quality of life. International guidelines recommend a stepwise approach to therapy with the inhaled corticosteroids as the most effective therapy for children with all levels of persistent asthma. Patients with intermittent disease (symptoms less than 2 times weekly) can be effectively treated with as needed short-acting β2 agonists. Leukotriene receptor antagonists and cromolyn/nedocromil are alternatives to the inhaled corticosteroids though not as effective. Children inadequately controlled on low daily doses of inhaled corticosteroids can increase the dosage or attempt adjunctive therapy with long-acting inhaled β2 agonists or leukotriene receptor antagonists. In infants and young children less than 5 years of age adjunctive therapy has not been studied. Both inhaled corticosteroids and leukotriene receptor antagonists reduce the risk of exacerbations in wheezing infants. Comparative studies have not been done. Attention has to be paid to delivery systems for aerosolized drugs in children and patient acceptance and compliance requires monitoring. Aerosolized drugs can be effectively delivered by MDI plus valved holding chamber spacer devices with a mask in or nebuliser and mask in young infants.