After the subcutaneous administration of tetrachloroethylene to rabbits by means of Fujiwara's reaction the author studied Fujiwara-reaction positive substance, the in vivo metabolite excreted in the urine of these animals; and obtained the following resultt. 1. Fujiwara-reaction positive substance in the urine is soluble in water, and in the presence of acid it is soluble in ethylether. The color tones and colorimetric findings of this substance are exactly identical with those of trichloro-aceticacid and likewise Rf in the paper chromatography rather coincides with the latter. 2. A considerable amount of the Fujiwara-reaction positive substance is excreted in the urine on the first day of tetrachloroethylene administration, and reaching its maximum on the second day but decreasing thereafter, the excretion lasts for 7-14 days. 3. In calculating this Fujiwara-reaction positive substance in term of the quantity equivalent to trichloro-acetic acid, its excretion percentage is 1.43-3.08 per cent, showing a parallel relationship between the total Fujiwara-reaction positive substance excreted in the urine and quatity of tetrachloroethylene administered.