Sodium cyclopentcnylallyl barbiturate known as cyclopal-sodium has been found to belong to the group of intermediate acting barbiturates. After intravenous injection of 80 mg. per kg. in rabbits the average duration of sleep, as measured by the duration of the absence of the righting reflex, is 114 minutes. A therapeutic ratio of 5.53 for male rats, 3.97 for female rats and 3.45 for male albino rabbits was found. A slightly lowered response was found after the second and following days when anesthetic doses of cyclopal-sodinm were administered daily over a period of time. Cyclopal is eliminated rapidly by some process of detoxication. Excretion plays practically no part in the elimination of this drug, since bilateral nephrectomy does not change the response to anesthetic doses. Accumulation occurs only when anesthetic doses of 60 mg. per kg. were repeated at intervals of two hours. Accumulation did not occur when doses of 30 mg. per kg. were administered at two hour intervals for twelve hours.