BACKGROUND: Mivacurium is mainly metabolized by plasma cholinesterase. However, the duration of action may be changed in various conditions such as liver dysfunction. To evaluate the action duration and recovery of mivacurium under the experimental acute renal failure, the pharmacodynamic studies were done. METHODS: The pharmacodynamic studies were done using a common peroneal nerve-anterior tibialis muscle preparation in 12, either sex, adult cats(weight 2.0~4.0 kg). The acute renal failure was made by the ligation of bilateral renal pedicles 1 hour prior to the pharmacodynamic study. All the cat received 5XED95 of mivacurium. The action durations and recovery indices were measured. And plasma cholinesterase activities were measured at each event. RESULTS: The duration of mivacurium was not prolonged with acute renal failure group(17.20 5.48 min.) compared to control group(13.48 4.30 min.). The recovery indices were not increased in the acute renal failure group(3.56 0.58 min.) as compaired with the control group(2.82 0.99 min.). CONCLUSIONS: The mivacurium-induced neuromuscular blockade is not prolonged by the experimental acute renal failure.