The appearance of an asthmatic crisis in the minutes following physical exercise is common in symptomatic asthma. Exercise induced asthma (EIA) is linked to hyperventilation; voluntary isocapnic hyperventilation is capable of triggering a crisis. It is well established at present that EIA and post-hyperventilation asthma (HIA) are triggered by a rise in heat and water loss by the airways, which is inherent in hyperventilation. The respective role of water loss and cooling the airways are uncertain but one tends to think at the present time that the primary stimulus is the variation in osmolality of the liquid lining the epithelium. However, a relationship between the quantity of energy dissipated in the airways and the severity of EIA or HIA exists, although it is less tight than was once thought. This is perhaps not surprising, as the intermediary mechanisms connecting the stimulus to the response of the airways are poorly understood. All in all physical exercise and isocapnic hyperventilation of dry air and possibly cold air are useful and equivalent non-specific bronchial provocation tests, if only the ventilation and physical properties of the inhaled air are the same. Hyperventilation lends itself better than exercise to establishing dose-effect curves linking bronchial response to minute ventilation. Recommendations concerning the interruption of drugs, the measurement of the response and the assessment of the results are the same as with other non specific bronchial provocation tests with irritant substances or pharmacological agents.