During the last decade, the prevalence of allergic asthma has increased in France, as well as in most developed countries. The clustering of symptoms of dyspnoea, chest tightness, wheeze, and their intermittent nature usually leads to a diagnosis of asthma. Nevertheless physicians should be aware of some atypical presentations such as recurrent infections, wheezing bronchitis, exercise induced dyspnoea or chronic cough. Physicians have also to recognize early symptoms of an acute severe asthma. For the identification of the allergen(s) responsible for asthma, data obtained from clinical history, from cutaneous prick tests eventually associated to serum specific IgE antibodies have to be taken in account. The assessment of severity of asthma is another essential point: it needs to be documented by using pulmonary function tests and in more severe forms of asthma on regular measurements of peak expiratory flow rate.