Scientific knowledge about general importance of nitric oxide has considerably increased. In the field of respiratory medicine this comprehensive research has achieved already very useful and practical form in diagnostics of asthma. Nitric oxide belongs to non-specific markers of inflammation. Despite the measurement of exhaled nitric oxide has only limited significance for diagnosis of asthma, it is very useful for monitoring of inflammatory process. This method is also suitable for the control of effectiveness of the antiinflammatory treatment. In some developing countries,measurement of concentration of exhaled nitric oxide in asthmatic patients is already used in fields between research and clinical practice. Author reviewed the recent information with the emphasis on clinical relevance.

        Key words: nitric oxide, exhaled air, asthma.