Spinal myoclonus is an unusual, self-limiting adverse event during the practice of spinal anaesthesia [1,2,3,4,5]. Although the exact etiology of medication-induced spinal myoclonus is unclear, it has been postulated that reduced activity of inhibitory mechanisms or increased excitability of facilitatory mechanisms at the level of motor neurons or interneurons is responsible [6]. We report a patient who underwent spinal anaesthesia with 2.5 ml of 0.5% hypobaric bupivacaine given by a 26 G spinal needle through the L4-L5 interval before operation for excision of a Baker's cyst in the right popliteal fossa. During the operation about 1 h after administration of anaesthesia, the patient began to have bilateral, symmetrical, rhythmic myoclonic movements in the lower legs. The severity and frequency increased gradually to approximately 20-30/ min.The operation was forced to be temporarily interrupted without suturing, and the patient was transferred to the recovery room. Throughout the event, the patient was conscious and oriented and vital signs were stable. The movements persisted despite administration of 10 mg diazepam IV followed by an additional 10 mg diazepam and 175 mg thiopental. The phenomenon persisted for approximately 50 min and resolved after recovery from spinal anaesthesia. Two hours after recovery from spinal myoclonus, the patient received general anaesthesia by IV administration of fentanyl (100 μg) and propofol (120 mg). The incision was cleanedup followed by suturing and disinfection. Subsequent neurological examination was normal, as were follow-up electromyography and EEG studies.