Various doses of pentobarbital (1.25-20 mg) and lidocaine (2.5-20 mg) were injected selectively into the artery of Adamkiewicz and anterior spinal artery of 11 monkeys. Pentobarbital produced an acute paraplegia; lidocaine caused a transient paraplegia followed by hyper-reflexia and muscular fasciculation. Duration of effect varied from 5 to 60 minutes with both drugs and was dose related. Effects were totally reversible. The use of intraarterially administered barbiturates and lidocaine may be more sensitive than angiography for predicting cord blood supply during arteriography for spinal arteriovenous malformations or embolization of critical vessels, such as the right bronchial artery.