Two cases are described transient unilateral paraplegia following a splanchnic nerve block (SNB) among 683 procedures in 708 patients from 1968 to 1992. The first case, 64 year-old male, had bilteral splanchnic nerve block twice with pure alcohol 4 months and 2month ago. The paraparesis of right leg was developed 4 minutes after the pure alcohol injection during the third SNB and was completely recovered after 37 minutes. The second case, 60 year-old male, had also a first SNB with temporary relief of pain for a week. The Second SNB with 95% alcohol was followed by paraplegia of left leg. He showed almost complete improvement but expired 18 days later. The probable cause was the spread of alcohol onto the lumbar plexus or paravertebral space unilaterally, because of adhesion or paravertebral space due to previous alcohol injections.