Two patients are presented in whom percutaneous radiofrequency spinal rhizotomy was complicated by contralateral paresis. Both patients were elderly and suffered from cardiac failure, chronic obstructive respiratory disease, and generalized vascular disease. Investigation of the paresis indicated a contralateral ischaemic cord lesion. It is suggested that local haemodynamic changes induced by heat-mediated rhizotomy may compromise oxygen delivery to the adjacent cord, especially in the presence of pre-existent cardiovascular disease.