Using the rabbits whose liver had been been injured with injection of 20% CCl(4) in oliveoil (1 cc/kg) every two days and administering parathion 24 hours after the third CCl(4) injection, the following results were obtained: 1) In rabbitts with injured liver serum cholinesterase activity reached its maximum 24 hours after the 3rd CCl(4) injection and returned to the original level, showing the improvement in the function of bromsulfalein excretion. 2) In the group with parathion injection 3 mg/kg each, serum cholinesterase activity was inhibited to the highest degree 3-6 hours after the parathion injection as in the healthy rabbits, but the slackening of cholinesterase activity in the injured was less marked than in the healthy, and lasted longer. 3) The LD(50) in the rabbits with injured liver was 3.88 (2.645.70) mg/kg, while the LD(50) in the healthy rabbits is 10 mg/kg. 4) In the injured rabbits parathion had no influence upon the recovery of the function of bromsulfalein excretion.