Idiosyncratic generalized skin disorders complicated by hepatitis, which resemble severe drug hypersensitivities, occur sporadically in workers exposed to trichloroethylene (TCE) in China. However, it has been a matter of controversy whether the solvent itself, not its impurities or stabilizers, can cause hypersensitivity reactions or not. This study aimed to characterize the exposure of hospitalized patients and their healthy colleagues. TCE metabolites were measured in urine of 19 hospitalized patients suffering from the disorders. To assess the exposure of patients' healthy colleagues, on-site surveys were conducted in 6 factories where the disorders occurred and in 2 control factories without such occurrences despite TCE use. Urinalysis of the patients detected trichloroacetic acid (TCA) in all of them. Its average concentration in the end-of-shift urine was estimated to be 206 mg/l. On-site survey of healthy exposed workers revealed that the maximum urinary TCA concentrations and the maximum time-weighted average concentrations of personal TCE exposure were 318-1,617 mg/l and 164-2,330 mg/m(3), respectively. There was no common impurity in TCE used in the factories. These results suggested that TCE itself caused the skin hypersensitivity disorders, and that the disorders occurred in factories where TCE metabolites could be extensively accumulated, possibly due to long working hours. Since the lowest TCA concentration in the end-of-shift urine of the patients was estimated to be 72-80 mg/l, it is recommended to control TCE exposure to keep the urinary TCA concentration below 50 mg/l to reduce the disease risk.