Background: The aim of the study was to analyze the data obtained during the diagnostic process and their real values in the final diagnosis of patients exposed to diisocyanates amd suspected of occupational allergic disease of the respiratory system The patients have been hospitalized in the Nofer Institute of Occupational Medicine over recent 11 years. Material and methods: In 1999-2009 we hospitalized 37 patients exposed to diisocyanates and suspected of occupational asthma. Results: Test results of 37 patients were analyzed. The patients were divided into three groups of those with diagnosed occupational asthma, with diagnosed non-occupational asthma and those without any allergic airway disease. 40.0% of patients with occupational asthma, 64.3% of patients with nonoccupational asthma and 15.4% of patients without any allergic disease were sensitized to at least one of common allergens. We did not find any specific IgE to diisocyanates. Specific challenge tests were performed in all the 37 subjects. We observed positive results of SIT with diisocyanates in 10 patients. Conclusions: Only specific challenge test with diisocyanates showed the real diagnostic value in case of a 7.5-year cessation of exposure. Determination of serum specific IgE to diisocyanates does not seem to be of clinical value in the diagnosis of diisocyanate-induced asthma in case of a 7.5 year cessation of exposure. Atopy is not the risk factor in diisocyanate-induced asthma. Med Pr 2011;62(6):567-577