The terephthalic acid (TPA) in the tissues of rat was assayed with radioactive terephthalic carboxyl-14C acid. Two groups were fed the diet supplemented with 0.5% of TPA for one and three days respectively, and TPA content in each tissue was determined. No difference was found between the groups. TPA per unit weight or volume, in kidney and liver was higher than in plasma but in the rest of the tissues was lower (8-10 μg in plasma, 40-50 in kidney, 16-23 in liver, and 0.4-4.8 in the other tissues). A single dose of TPA was distributed rapidly in the tissues within 2 hr, and the ratios of TPA contents in the tissues showed the same tendency as the above case. The maximum contents of TPA in the tissues were observed within 2 hr after administration, while in brain after 8 hr. In the both cases, three-day feeding of the TPA diet and single oral administartion, a little amount of TPA was found after 24 hr only in several tissues. It already disappeared in more than half of the tissues. The biological half-lives of TPAs in the tissues, 1.2-3.3 hr, were calculated from the result of single oral administration. It is concluded that terephthalic acid is rapidly eliminated from the tissues and not accumulated in any of them.