Different methods are available to measure non-allergic airway responsiveness. In the last years, efforts have been made to improve standardization of these methods, in order to allow comparison of data from different sources. The most currently used bronchial provocation tests are those with nebulisation of histamine or methacholine either a tidal volume or from a dosimeter, a dose-response curve being obtained in measuring expiratory flows or airway resistance. Inhalation of non-iso-osmolar solutions, cold air hyperventilation, exercise or other agents and stimuli may be used to estimate airway response, but they are more useful as a research tool than for clinical purposes. The reproducibility of bronchial provocation tests is dependent of different factors such as those related to the subject (asthma stability, performance of tests, medications, circadian variations), technical factors (type and calibration of the apparatus, nebulizer output, measurements, solutions) and to the methods of calculation of the bronchial response. Short-term reproducibility of the different types of bronchial provocation tests is usually good although long-term stability needs to be further assessed. A correlation has been reported between the response to most of the different bronchoconstrictor agents, although variable.