Objective: To study the e cacy of intrathecal ethanol block to relieve intractable spasticity in AIDS-related progressive multifocal leukoencephalopathy (PML) when long-term intrathecal baclofen infusion cannot be used. Methods: A 33-year-old man with AIDS-related PML developed very severe spastic paraparesis (Ashworth rigidity score, 4) and painful muscle spasms. The patient was unable to sit in his wheelchair and remained bed bound. Combined oral baclofen and tizanidine at therapeutical doses were used without any e ect on the spasticity. The patient refused the placement of an intrathecal catheter for long-term baclofen infusion. A single intrathecal ethanol (6 ml) injection in the L2-L3 intervertebral space with the patient placed in a lateral Trendelenburg (408C) position was performed. Results: The procedure was very e ective in improving the sti ness (Ashworth rigidity score, 2, after the technique) and the muscle spasms disappeared. No side e ects during or after the injection were observed. Conclusion: Intrathecal ethanol block is a last but very useful choice for treatment of intractable spasticity in PML and other neurologic disorders in AIDS patients when other oral treatments have failed and intrathecal baclofen infusion is not suitable.