Objective 　To investigate the factors associated with long-term efficacy of microvascular decompression for hemifacial spasm. Methods　253 cases of hemifacial spasm treated with microvascular decompression were followed 13 to 144 months (mean 73 months). Results　Hemifacial spasms were obliterated in 232 cases (91.7%) and were partially relieved in 10 cases (4%). However, hemifacial spasm recurred 11 cases (4.3%). We re-operated on those who had recurrent hemifacial spasm and found that the material used for previous decompression had moved. The movement of decompression material could be the cause of spasm recurrence. Conclusions　Upholding of depression material around the blood vessels against movement near the facial nerve plays an important role for improving the long-term efficacy of MVD for hemifacial spasm.