Asthma and COPD (chronic obstructive pulmonary disease) are the most important obstructive pulmonary diseases. Patient's history and physical evaluation give major hints of the underlying disease. Further diagnostic measures comprise lung function analysis including spirometry, plethysmography and--in severe cases--blood gas analysis. Bronchial hyperreactivity may be quantified with an unspecific inhalative provocation test. In many cases allergic diseases are accompanied by asthma. Thus, allergy tests--particularly skin prick tests--have to be carried out. To further define an underlying allergy, in some cases even specific inhalative provocation tests have to be performed. X-ray of the thorax and other imaging techniques, detailed blood analysis, further diagnosis of the upper respiratory tract and the cardiac system may have to be carried out a) to quantify the effects of a severe form of asthma or COPD on other organs, and b) for differential diagnostic examinations.