We investigated the working conditions of a dry-cleaning shop where they had previously used trichloro-ethylene but after the renovation of the shop they now use tetrachloro-ethylene instead and obtained the followlng results. 1. The concentration of tetrachloro-ethylene in the air at the time, when washers were open, was found to be 200-250ppm, surpassing the maximum allowable concentration and the average concentration in the air was, however, 25-30ppm, showing a distinct decrease as compared with the concentration of 420ppm near the washers at the time when they had used trichloroethylene. 2. There could be detected Fujiwara's substance in the urine of employees and assuming the substance to be trichloroacetic acid, it was found in the quantity of 14.5mg/l, which, compared with 416mg/l of trichloro-acetic acid, detectable at the time when they had used trichloro-ethylene, was clearly less. It is assumed that one of the factors bringing about such a decrease, is due to the inhalation of lesser amount of ethylene vapor by the the use of less volatile tetrachloro-ethylene in place of trichloro-ethylene. 3. Judging from the Rf value of paper chromatography and absorption spectra of Fujiwara's reaction, it is assumed that Fujiwara's-positive substance in the urine of employees has the chemical structure similar to one of trichloro-acetic acid. 4. In the serum proteins of the employees there could be recognized a diminution of albumin and an increase of β-globulin by paper electrophoresis, in their colloidal reaction an increase of cephalin-cholesterol reaction and the right shift in the cobalt reaction, and an increment of the urinary urobilinogen content. These results seem to indicate a slight disturbance in the liver functions of the employees as the result of their employment for 6years while using trichloro-ethylene and working in the shop for 4years since they began to use tetrachloro-ethylene.