Using a self-made bag inhalation challenge device. We diagnosed 12 TDI asthmatics, who were from 18 symptomatic workers. Of the 12 cases there were three types of airway reaction to TDI: three showed an immediate response; six, a late response; three, a dual response. After inhalation challenge, FEV1 PEFR, V50, and V25 descended obviously, suggesting that airway response to TDI in TDI asthmatics might occur in either larger or small airway. As a result of methacholine challenge nonspecific bronchial reactivity in 12 TDI asthmatics was markedly increased. After inhalation of TDI, the further descending of PC20 FEV1 showed that TDI could increase airway reaction to methacholine. Patients received skin test with TDI-HSA conjugate. There were positive response in 11 of the 12 TDI asthmatics and in 11 of the 62 TDI workers who had no symptoms after exposure to TDI, and no positive response in 18 common asthma patients. Therefore, TDI-HSA skin test can be used to a assist diagnosis of TDI asthma and a differential diagnosis from ordinary asthma. Specific IgE antibody levels showed no difference between TDI asthma and normal control group before TDI challenge. A marked increase in TDI asthma occurred after TDI challenge.