Unilateral ventrolateral (VL) thalamotomy for medically refractory tremorigenic movement disorders (MD) was performed in 9 patients with established multiple sclerosis. All patients had abolition of their coarse action/kinetic tremor with improvement in arm and hand function. In two patients some intention tremor either remained or was unmasked. Target coordinates ranged from 2 to -5 mm relative to the intercommissural line and from 8 to 16 mm lateral to the midline. There were no permanent surgical complications and the one stage procedure under local anesthetic was well tolerated. Although there were also improvements in posture and speech in some patients the overall and longer term functional impact of surgery was, except in two patients, disappointing. Since multiple sclerosis is a spectrum of disease entities, and tremor may be only one manifestation of the disease, clinical studies that use comprehensive patient assessments and objective criteria may allow prediction of longer term functional outcome in specific patient subgroups. The specific aims of the stereotactic procedure in severely disabled patients with MS and MD must also be clear.