Halothane in tissues of the rat has been measured as a function of time after five successive 3 hr exposures to 670 ppm halothane. In epididymal and perirenal fat, halothane concentrations diminished rapidly from 310 ppm to 1–2 ppm in 24 hr, with trace amounts detectable 5 days later. Brain and liver levels were reduced from 16 and 9 ppm to less than 1 ppm within 3 hr. Blood halothane was reduced from 3 ppm to less than 0.5 ppm in the same time.