Succinylcholine (Sch) has long been used to facilitate laryngoscopy and endotracheal intubation for general anesthesia, because of a rapid onset of intense but brief paralysis. However, exaggerated potassium (K+) release following Sch, sufficient to cause ventricular dysrhythmias and cardiac arrest, has sporadically been reported in susceptible conditions, including spinal cord injury, severe burn, massive trauma and neuromuscular disorder. And diazepam has been shown to attenuate the increase in serum K+ following Sch administration. The purpose of this study was to assess the effect of Sch on serum K+ in patients with spinal cord lesions, and to assess the effect of pretreatment with diazepam (0.05 mg/kg IV) on potassium flux. The results were as follows: 1) Baseline K+ values were not significantly different among the groups. 2) The time to peak increases in K+ was 3 minutes following Sch in all groups. 3) The magnitude of maximum increases in K' following Sch were 0.32 Eq/l, 0.63 mEq/l, 0.06 mEq/I and 1,10 mEq/I in group 1, group 2A, group 2B, and group 3, respectively. 4) Diazepam pretreatment attenuated the increases in K+ following Sch. From the above results, it can be concluded that Sch may safely be used to facilitate intubation in paraplegic patients, provided that they are normokalemic and pretreated with diazepam.