Occupational asthma is one of the most frequent occupational diseases of the respiratory tract in developed countries. Moreover, the diagnosis of occupational asthma is difficult because the confirmation of the occupational origin of the disease has an important impact on the career of the employee and many persons must involuntarily leave their work position. To avoid serious consequences, it is necessary to develop new methods which could disclose the incipient occupational asthma earlier than methods available nowadays or support the diagnosis in case of equivocal results (decrease in ventilatory parameters) of the bronchoprovocation tests. Exhaled breath condensate (EBC) analysis is a new non-invasive method which appears useful in occupational asthma diagnostics. Leukotrienes as obstruction markers and 8-isoprostane as an oxidative stress marker could be analysed from EBC. The concentrations of leukotrienes and 8-isoprostane were described to be elevated in EBC of asthmatic persons. Monitoring of leukotrienes and 8-isoprostane concentration changes in the EBC during the bronchoprovocation tests with allergens could bring new information about the pathophysiological changes in airways during inhalation tests with allergens. Induced sputum is a relatively non-invasive method which could be used in asthma diagnosis. The monitoring of the sputum cell count (especially changes of eosinophils) has a potential to be used for monitoring of asthma and during allergen challenge tests, too. The elevation of sputum eosinophils was described after allergen tests in several studies.