In a single and repeated exposures to trichloroethylene, the behavior of urinary trichlorethanol (TCE) and trichloracetic acid (TCA) in rats was investigated. In the single exposures rats were exposed to 200 ppm of trichlorethylene once for 3 hours, and in the repeated exposures rats were exposed to trichlorethylene at the same concentration for the same hours on 5 successive days. The results obtained were as follows: 1) In rats exposed once most of the urinary TCE was excreted within 24 hours after the beginning of exposure, whereas the urinary excretion of TCA continued for 4 days. 2) In repeated exposures, the urinary excretion of TCE reached a maximal level following the second exposure and remained constant thereafter. In contrast to this, the urinary excretion of TCA increased continuously from the first day to the fifth. 3) The ratio of TCE: TCA showed a decrease from 2.8 in the first day to 1.2 in the fifth day of the repeated exposures.