After the subcutaneous injection of a given amount of trichloroethylen to rabbits, the author estimated colorimetrically the quantity of trichloroethylene exhaled from the lung by Jacobs' method with the use of an electrospectrometer; and obtained the following results. 1. The quantity of trichloroethylene exhaled increases rapidly one hour after the trichloroethylene administration, and it reaches the maximum three hours afterwards. The increase during this period draws a straight line, and thereafter decreasing gradually in a curve, the exhalation ceases by 24 or 28 hours later. 2. The total trichloroethylene exhaled amounts to 39.4 to 58.7 per cent of the quantity injected, showing an approximately parallel relationship between the two.