Background:  Toluene diisocyanate (TDI)‐induced asthma is a common cause of occupational asthma and it affects 5–15% of the exposed population suggesting an underlying genetic susceptibility.Methods:  To investigate the role of genetic factors in the development of TDI‐induced asthma, we analyzed the distribution of human leukocyte antigen (HLA) class I genes and of tumor necrosis factor (TNF)‐α A‐308G polymorphism in 142 patients with TDI‐induced asthma and in 50 asymptomatic exposed subjects.Results:  Neither the distribution of HLA class I antigens nor the distribution of TNF‐α A‐308G polymorphism was different between patients with TDI‐induced asthma and asymptomatic exposed subjects.Conclusions:  These results suggest that HLA class I antigens and TNF‐α A‐308G are not associated with susceptibility or resistance to the development of TDI‐induced asthma.