Allergic bronchopulmonary aspergillosis (ABPA) associates the development of aspergillus in bronchus and a predominant immediate hypersensitivity for aspergillus antigens. It complicates an old and severe allergic asthma or cystic fibrosis. Its prevalence is not well known. In children, ABPA prevalence is rare, except in cystic fibrosis where 0.6% to 11% of patients can be affected by the disease. Acute exacerbation of the disease favours the development of bronchiectasis and fibrosis. The diagnosis is suggested by an unexplained aggravation of asthma or, in cystic fibrosis, by wheezing, an unsuccessful antibiotherapy, and a recent modification of the chest X-ray. The diagnosis is based upon the presence of seven major criteria or six major criteria and one minor. The follow-up of biological parameters is important for early diagnosis of exacerbations. Some parameters are very sensitive, ie, precipitins and total serum IgE. Systemic corticotherapy is the usual treatment of exacerbation. The association with inhaled corticotherapy could reduce the duration of systemic treatment. The use of Itraconazole is logical, mainly in cystic fibrosis.