The clinical investigation of occupational asthma is currently based on the demonstration of functional changes after exposure to occupational agents, but it does not yet include any monitoring of airway inflammation, one of the hallmarks of this disease. Methods permitting a non-invasive assessment of airway inflammation, such as induced sputum and exhaled nitric oxide, are currently under investigation for research purposes in occupational asthma. Their role in clinical practice has not yet been established. The advantages and limitations of these methods for occupational airway diseases, and more particularly occupational asthma, are discussed in this review.