An appreciable number of patients with toluene diisocyanate (TDI)-induced asthma have high serum levels of specific IgE (sIgE) antibody to TDI-human serum albumin conjugate (HSA). A recent investigation suggested a role of specific IgG (sIgG) in the development of TDI asthma.We observed the changes in the levels of specific IgE and IgG antibodies to TDIHSA conjugate in TDI-induced asthmatic patients during seven years avoidance.Six subjects with high sIgE and five with high sIgG were enrolled. All of them had taken anti-asthmatic medications with complete avoidance. Serum levels of sIgE and sIgG to TDI-HSA conjugate were detected by ELISA. The level of sIgE continued to decline up to 7 years and the mean half-life was 3.9 years. The mean half-life of sIgG was 4.5 yrs.These findings suggest that both sIgE and sIgG to TDI-HSA conjugate may persist for several years after the last exposure to TDI.