Terms exercise-induced asthma (EIA) or exercise-induced bronchoconstriction (EIB) are used to describe transient bronchoconstriction occurring during or immediately after vigorous exercise in some subjects. For the diagnosis of EIB it is necessary to show at least 10% decrease in FEV1 from baseline following physical exercise. The prevalence of EIB has been reported to be 12-15% in general population, 10-20% in summer olympic athletes, affecting up to 50-70% of winter athletes (particularly ski runners and skaters). There are two key theories explaining EIB: thermal and osmotic. Differential diagnosis of EIB should include chronic cardio-pulmonary diseases, vocal cord dysfunction, hyperventilation syndrome and poor physical fitness or overtraining. According to the ATS guidelines from 1999 for the diagnosis of EIB a standardized exercise on a treadmill or cycle ergometer test with stable environmental conditions regarding temperature and humidity of inhaled air, should be employed. Other laboratory tests assessing bronchial hyperresponsiveness to indirect stimuli including eucapnic voluntary hyperpnea (EVH), mannitol, hypertonic saline, AMP or measurement of exhaled nitric oxide (FENO) are also successfully used. In the prevention of EIB include both pharmacologic and non-pharmacologic treatment. In patients with poorly controlled asthma intensification of anti-inflammatory treatment can decrease the frequency and severity of EIB. Short and long acting beta2-agonists, antileukotriene drugs can be used prior to exercise to prevent EIB.